1. Lets say I want to record the section in 4/4 but in specific measure I want to change it to 3/4 and after that return to 4/4. Is it possible and how?

You don't. All measures of a Pattern Section must be in the same time signature. You will need to record your 4/4 measure or measures in one Section, and your 3/4 measure or measures in a separate Section.

When working with multiple time signatures, I find it useful to construct the composition using the Song mode, rather than Pattern mode. My reason is simple, I can "teach" the Song sequencer my "chart" prior to recording. Song mode is linear in nature so when I have a composition that has multiple time signatures and/or tempo changes, Song mode is the better tool. You can create a Time Signature and/or Tempo map prior to playing into it.

The CREATE MEASURE Job (found in SONG mode) allows you to create as many measures as you need of the supported time signatures prior to entering Record. MIDI convention fixes the default time signature to 4/4; Every measure in the Midi a Song entity is individually programmable, but each defaults initially to 4/4... so basically you create the number of measures you need of your alternate time signature at the appropriate Measures in the linear layout. The Sequencer's click (metronome) will then faithfully adjust its count to reflect your time signature map.

If you require Pattern mode for performance purposes, you can then use the JOB: "Split Pattern to Song" to divide your Song into Pattern Sections, remembering that a Section of Pattern mode must be in a single time signature.... Isolate you 3/4 measures to separate Sections.

2. How do I add inserts effects to each track?

Again, the answer is: you don't. A "track" is a part of the sequencer. Tracks contain only MIDI data, like note-ons, controller commands, etc. Yes, we are being picky about the wording, only to make the point of how to go about thinking this through on your own. The Effects in this type of system are added to the tone generator Part. The synthesizer tone engine makes sound, therefore the effects are inserted on the synthesizer engine.

The workstation (or music production) synthesizer combines a Synth tone generator, a Keyboard controller and a Sequencer... Back in the day when these were 3 separate devices interconnected by Midi cables it would have been clear which device you would go to to add insert effects. The Synth is the only one of the three devices that makes any noise... And therefore you knew immediately Effects would be assigned there...

That point made, any eight Parts of your Pattern (or Song) Mixing setup can recall their dual Insertion Effect. You can select which 8 Parts as follows:

From PATTERN
Press [MIXING]
(If you "edit" from Pattern you see sequence events. If you "edit" from Mixing you see the synth...)
Press [F6] EFFECT>
The > arrow after the word "Effect" indicates this is a shortcut to take you directly into EDIT.
In this case to the EDIT > COMMON > [F6] EFFECT > [SF1] CONNECT screen
Press [SF2] INS SW (Insertion Switches) here you can set a maximum of eight Part ON. "ON" allows the Voice assigned to this Part to recall its two pre-assigned Insertion Effects. Only 8 ON switches can be activated at any one time. And in order for a Part to have Insertion a Effects this must be activated.

If you would like to edit, or change the two pre assigned Effect Type simply:
Press [EXIT] to return to the Mixing screen
Select the PART you would like to work with
Press [F5] VCE ED> (Voice Edit)
This shortcut takes you into full Voice Edit on the normal (non-drum kit*) Voice assigned to this Part. Now as if you were actual in VOICE mode, you can deeply edit this Voice, even changing the two pre-assigned Insertion Effects.

*We should mention you cannot edit Drum Kit Voices using this shortcut on the front panel of the MOXF... Normal Voices are just 8 Elements so routing is simple in comparison to the 73 individually routeable Elements in the drum kit Voice. If you wish to edit the drum kit, please use the Yamaha MOXF Editor Standalone/VST. The MOXF simply does not have enough memory to juggle all the possible routing onboard... It's available, just simply exit your Mixing and return to Voice mode to edit drum kits, or boot up the Editor which will allow you to edit in context of your Pattern.

Hope that helps.

Hi, I also have related questions to this:

This shortcut takes you into full Voice Edit on the normal (non-drum kit*) Voice assigned to this Part. Now as if you were actual in VOICE mode

If I edit a voice in mixing mode, it seems that just editing the voice and then storing that song doesn't keep the changes I made. If I later recall the song, the voice is in its original state again. If I want to keep the changes I have to store it as a mixing voice.

If you wish to edit the drum kit, please use the Yamaha MOXF Editor Standalone/VST.

So if I got this right, with the Editor it IS possible to edit a drum kit for a particular Song. Are these edits kept when I store that song or can I use Mixing voices to store edited drum kits too?

Is it also possible with the Editor to edit voices/drum kits while a song is playing? Couldn't try it out yet as I'm still waiting for my new PC which I'll connect to the MOXF 😉

So if I got this right, with the Editor it IS possible to edit a drum kit for a particular Song. Are these edits kept when I store that song or can I use Mixing voices to store edited drum kits too?

Drum Kits are too big to be contained anywhere but in its own special Bank. Only so called "normal" Voices can be stored locally as a MIXING VOICE.

A normal MOXF Voice has but 8 Elements (Oscillators). A Drum Kit Voices contains 73 Elements, one per key C0~C6. So it the size of the drum kit Voice that is the reason you cannot edit it on-board the MOXF, and is also the reason it must be stored in a dedicated User Drum bank location. The routing per drum is extensive. Each drum key is autonomous, as to its routing through one or the other of the two available Insertion Effects (or neither), each has its own Send to the System Effects, its own Filter, its own AEG, its own volume, panning, etc., etc. etc. drum kits are extremely complex. So rather than cripple it, you must treat it as special... Because it is!

One of the things you CAN do in the Motif XF is edit the drum kits in place, but even with the Motif XF you must store the Kit in one of the 32 User Drum Kit locations in the dedicated User Drum Bank. It's just so flexible and complex it demands its own bank of locations.

Editing the Drum Kit can be done with the MOXF while in context, with the assistance of the Editor... Yes while the song is playing!