First, is it correct that sort/ separate job only works if all notes forming the chord I want to sort all fall on the same clock tick. If so, Its probably then a good idea to always check this first before proceeding to sort and separate anything.

Correct... there is window on ether side of the beat that qualify it as being a chord, but generally, Quantize > Chord Sort > Chord Separate is the recommended workflow.

Second, If I don't like my note spacing, I cannot simply enter a new spacing, correct?

You can, simply “Undo” the Chord Separate, Change your setting, and execute. Undo always works on the last executed Job, allowing you to hear the data AFTER execution, and then Undo returns it to the way it was just BEFORE the Job was executed. (A-B)

Finally, maybe you can advise any easier workflow for the following strum pattern. I am working in 3/4 time trying to get, in every measure, a quarter note downstroke followed by three eighth note up/down/up strokes. This same strumming pattern repeats with a 4 chord progression running through 16 measures. So far, I have not been able to get it done right in one job. Do I need 32 jobs to do this? Or, could I do all the quarter notes first, then overdub the eighth notes and perform a separate sort/separate job for just the three eighth notes measure by measure? That would mean 18 jobs.... I am guessing I cannot sort and separate over any prior sort/separate jobs, without disturbing those prior jobs, correct?

If you have concluded that manually creating strums is a lot of work, you are correct.

Last time that I worked with this Quantize > Sort > Separate Function was back on the QX3 (circa 1989 or 90)... I recreated some funk rhythm guitar riffs, in the style of my friend, Nile Rodgers... took hours, but back then there was no other way to do it, and so it wasn’t a matter of finding an alternative... besides I wanted to show how these Job features could be put to good use. So, yeah, it’s a heck of a lot of work... and then to make it sound more realistic, I needed to create some changes in the length of some of the chords .

The QX3 could create a macro (memorize a series of button presses) so it was possible to, after stepping through the Jobs, select a region and then hit the execute button... but to really get something that’s accurate, it’s a lot of work.

If that is an issue for you... then invent a different method. When all is said and done, remember YOU hear things differently than non-musicians. We know a guitar does not hit all the notes of a chord simultaneously, musicians hear that because we know and perhaps that is why we can hear it. I can only speak generally, because I can’t hear the guitar Part you are creating.

Strums can vary from where only the “trained” ear hears the up versus the down stroke... to where because of timing and tempo, everyone can hear the up versus down stroke.

Alternate Methods (that can be quicker):
Use Step Record.
You can set the Step size small enough to make entering down strokes and upstrokes easier.
Say you decide that 6 or 10 clock ticks is the separation that works.

Move to the appropriate beat, set the Step size and enter the downstroke by hitting the lowest note first, using one note-on at a time to outline the chord.
For upstrokes move to the appropriate beat and enter the highest note first, using again one note at a time method to enter each note one after the other.

As you get really good at this, (if I remember correctly) you can have the ES Sequencer Capture the Key Velocity so you can really make it sound like a strum. (All Notes on a guitar are not always the same Loudness. The “Value” parameter sets the Velocity... set that to KBD, and it will read how hard you hit the keys.

Phil, Your last short step recording alternative is great option..... To take full advantage of this can you please check my understanding of downstrokes and upstrokes on say a six string guitar? If I want to replicate a downstroke of say a C chord, that means I need to figure out the notes strummed starting from top string to bottom string. As a job function within SORT CHORD on my ES - "down" defines downstroke as organizing all notes in descending order - high to low..... but are true strummed guitar chords always that linear either high to low ("down") or low to high ("up")? I am thinking NOT, and that's why your step recording suggestion seems to be the best / only way to get an accurate reproduction. Is my understanding correct?

You should do your own interviews with guitar players, but a “strum” is either low to high string (downstroke) or high to low string (upstroke), any other direction would have a different name for the gesture. A strum, while it can have many different executions due to speed, I believe a strum is defined by upstroke or downstroke based on the strings being triggered one after the other in the direction played.

Strums on banjos and ukuleles would be different because the order of the strings is not a simple ascending map.
On a guitar a downstroke is low string first, while an upstroke is high string first. However, bluesman Albert King would string his guitar opposite of most players so for him a downstroke was high string to low string!

Thanks for taking the time to talk guitars on keyboard. You mentioned the Uke strings...Coincidentally it was when I was strumming my uke earlier that I discovered that chords I strum on the uke are not in straight ascending or descending order. That's what prompted my followup question.

Let me just return to the ES manual p.229 to clear up the ups and downs of the sort function. If a guitar downstroke generally means low string first - that's ascending, correct? Of course the hand stroke motion goes down across the strings but the notes played ascend up, right?. However the "down" setting on the ES sorts in descending order , from high to low (like a guitar upstroke) and calls this a downstroke strum? I am confused. It seems like the ES has it reversed to normal guitar strum voicing, No? This might now be just academic now for me because your step record option will probably be a better workflow solution for me when programming strums. Nevertheless, I still want to understand the terminology and voicing of the sort chord settings. I can't begin to tell you how much time and head scratching I spent trying to get the sort chord function to sort as I expected....does up really mean down?

Don’t make it more complicated than real life!
A downstroke on a guitar is called that because you are gesturing (down) toward the floor... and yes, on everyone’s guitar (except the aforementioned, Albert King) that is going up in pitch.
An upstroke on a guitar is called that because the gesture is upward toward the ceiling... and yes that direction goes down in pitch on a guitar.

When holding a standard tuned guitar the low strings are high (ceiling), and the high strings are low (floor).

Does the parameter say “up” and “down”, or “upstroke”/“downstroke”? Don’t over think it... these are known facts.
Because the edit Job is not only for creating Guitar strums (what you are doing), up and down seem the most appropriate terms... When you conclude that what you are doing at the time is the only way a feature can be used - is when you get in trouble. Chord Separate could just as easily be used for creating Harp flourishes, Keyboard runs, a hundred other things.

If the job was called “Guitar Strums” then the terms up/down would be better replaced with downstroke and upstroke, but the job is generic - therefore it makes sense to describe the actual direction the data is going. Make sense?

I get what you are saying but the manual combines note direction and "guitar-like" stroke to define what each sort function does. UP is described to sort as ascending notes creating guitar like up strokes. Down is described to sort as descending notes creating guitar like down strokes. I wanted to make a down stroke, i.e. ascending notes which is written in UP definition. However, UP made my notes go high to low instead of low to high. Trial and error, I know now that the sort parameters UP or DOWN mean direction of hand gesture across guitar strings, NOT the direction of the pitch of the notes. I think I also discovered (please check me) that by default, in step recording, all notes pressed to the same clock tick, when released are then automatically entered as note events from low to high pitch, meaning, by default step recording sorts notes in ascending order as a downstroke, no need to perform separate sort job for this. Whenever I want a downstroke using step recording, just press the chord, separate and go, correct?