That sounds mostly correct. The “Favorites” is a function of the Category Search engine, not the Data Utility or Library Import function.
The MODX is the only place you can play the Performances, you cannot play the Performances in the Waveform Editor.

Perhaps you are confusing the Waveform Editor’s ability to manipulate the custom Waveforms, Samples and Arpeggios, so that you can completely construct your File *offline* (in the computer) then when you create the File it will contain all the data.
You can click on a Waveform and have it sound, but you cannot — but you cannot “play the Performances”... for that you need a MODX or MONTAGE.

It is highly recommended (if you cannot remember which Performances you want to keep...) that you write them down. This way you can refer to them. It is necessary that you mark all the items you wish to “import” to your User Bank (New Library) in one operation. This way the MODX can sort out and eliminate duplicates.

What this means is... if several Performances in the CS80 Library use the same Waveforms, if you IMPORT them in a single operation, MODX can sort out what Waveforms go where, and will not duplicate any waveforms. But if you import each Performance separately, the MODX will import the Waveforms each time.

If you have the Waveform Editor assembling a new Library from old data is as easy as dragging the items you want into a blank Library and saving it as a .X8L File. You can open multiple Libraries simultaneously, and just drag the items you want into your new template.

When finished you will have a File you can install to your MODX.

Alright, thanks, guess there's no avoiding doing some manual work here!

Would be very convenient if you could view favorites when doing the library import, or even better, automatically import everything in the library you have marked as a favorite, but we can't have it all I suppose.

Without adding external software, load the entire library first then use the Library Import feature to choose which ones you want to keep. Before library import, make a backup of your user area (X8U file) so you can initialize only the user area (wipe the user bank clean). This way you are importing FROM the library TO the user area which is empty at the start. Save your user area to a new (customized/trimmed) library X8L file. Then delete your source (big) library you initially loaded to MODX. And last, load the customized/trimmed library into a library slot.

I really chimed in to make this point: trimming a library may have zero impact on the amount of waveform memory consumed. As an example - say I had a made up library with 4 Performances.

Performance 1: Analog Synth (Called "Space Synth" )
Performance 2: Analog Synth w/wah (Called "Ghost Synth" )
Performance 3: Transistor Organ (Called "Far Out" )
Performance 4: Transistor Organ w/Delay (Called "Bounce About" )

Now I made the performance names intentionally obscure what the Waveforms are for each - but performance 1 and 2 use the same Waveforms and performances 3 and 4 use the same Waveforms. The main differences are in effects. Effects do not consume any waveform memory.

And say I decided "Ghost Synth" (perf 2) and "Bounce About" (perf 4) weren't my cup of tea - so I decided to delete them. Now my library would contain 50% of the Performances. However, since deleting both did not delete any Waveforms completely (Perfs 1 and 3 still point to two different sets of Waveforms) -- my trimmed down library will still consume the same amount of waveform memory as my original library. The benefit of the trimmed library is just less "fluff" to scroll through when searching - but there is no benefit in terms of memory space.

It's conceivable that there's another made up (but possible) library that is 100% pianos. "Pianos Galore". With every piano under the sun in every kind of setting. And the library uses all 640 possible Performances in a library (640 different pianos). And the programmers decided to use the same exact samples (Waveforms) for every single piano - but used other non-sample programming to alter the sound of each performance (different effects, ADD2R - aka ADSR, different combinations w/strings and other factory sounds). This imaginary library you can delete 639 Performances - leaving just one Performance - and your resulting 1-Performance Library would consume the exact amount of Waveform space as the original.

Thanks, yes, I'm aware of that. But I'm pretty sure both of the libraries I'm talking about here do use quite a few different waveforms for different performances, so cutting out what I don't need should save me some space. With the Bösendorfer library it wouldn't.