Hi ab,
Welcome to YamahaSynth! Thanks for the question.

OK, I have created a drum kit from my wav samples. Then I save it to Library file to usb stick.
I clean synth memory and install this Library file successful. Now I haven't waveforms in folder!
Only monolith one block the Library file. It's good! But when I need to tune settings and save
to new Library file the output file is few kilobytes! Second file don't contained samples data. Why?

The Waveform Folder will show you what is currently in your USER Bank.

As you have said, you installed your Drum Kit waves into a Library. Your samples are now in the ROM Library.
There they will remain until you manually DELETE them, you “Initialize All Data” or you overwrite your entire instrument with BACKUP File (.X8A).

What's different User file or Library file? User doc don't have deep understanding this.

This is the key to this whole thing.

A USER File (.X8U) when loaded to the MODX will replace all data in the User Bank with the data from that file.
When you load data from a User File it can contain as many as 640 Performances, 2,048 Waveforms, 256 User Arps, 256 Motion Sequences, 8 User Live Set Banks of 256 slots each. This is the data that occupies some of the “Data Utility” Folders

[UTILITY] > “Contents” > “Data Utility”
The folders are listed alphabetically; here is what they contain.
Arps - contains the current User Arpeggios, up to 256
Library - contains your currently installed Libraries (8 slots)
Live Set - 8 Banks of User Live Sets; each Set list can contain 256 steps
Motion Sequences - contains the current User Motion Sequences, up to 256
Pattern - any .mid data you create with the Pattern Sequencer or any .mid you load to the Pattern Sequencer will remain in this Folder until you manually delete it, you “Initialize All Data” or you load a BACKUP File that replaces all your data
Song - any .mid data you create with the MIDI Song Sequencer or any .mid you load to the MIDI Song Sequencer will remain in this Folder until you manually Delete it, you “Initialize All Data” or you load a BACKUP File that replaces all your data
Waveform - any User Waveforms you have loaded into the MODX.

When you load a .X8U User File from a USB stick, you always receive a warning - that the current User Bank will be overwritten.
This means the Arp folder, the Live Set folder, the Motion Sequence folder, and the Waveform folder are all overwritten with the Arps, Live Sets, Motion Sequences, and Waveforms from this new File. When you load a User File it’s User data occupies those folders — this is where you can manage this data.

If you have created any new Arps, any new Live Sets, any new Motion Sequences, or added any new Waveforms, this warning is FOR YOU, it is a reminder to save a .X8U User File before proceeding. Once you do, you can load a different User zfile. If you have created nothing new, then overwriting it is no big thing. If you already have a file, no big deal. When you want to restore that data just load it.

So what’s a Library File?
When you Load a Library File it goes directly to Flash memory - where it is installed (burned into ROM). The Library File .X8L has instructions to burn the data in to Flash ROM. This means the data will be there at all times - just like the Factory Performances, the Factory Waveforms, the Factory Arpeggios, the Factory Motion Sequences, and the Factory Live Sets. They remain as long as you want them there...

How do you create a LIBRARY File?
The Library File is equivalent of one complete USER Bank... if you were set the User Bank in stone, that’s what becomes a Library.
You can freeze 8 copies of your User Bank... that’s the 8 Library locations.

It is very much a SAVE AS... routine... You might take a Word document and SAVE AS... a PDF.
The Word document is like a work in progress (like the User Bank) and the PDF is like the finished form of the document ready for publishing (Library).

When you look at an AWM2 (Sampled Part), go to Edit > select an Element along the bottom of the screen
On the “Osc/Tune” screen the Waveform is going to come from one of three BANK locations:
_Preset - there are some 6,347 Preset Factory Waveforms permanent ROM
_User - there is room for 2,048 User Waveforms in the User Bank memory (this memory is susceptible to being overwritten)
_Library - there is room for 8 Libraries - the Waveforms in a Library are in Flash ROM

You create a Library by assembling your data (Performances, Waveforms, Arps, Motion Sequences, Live Sets, etc. in the USER BANK.

Say you didn’t fill all 640 possible Performances, nor did you use all 2048 Waveform slots when you made your Library of Drum Data... and you want to add new Performance and maybe some more Waveform data to that Library...
well, you can’t while it is in Flash ROM (Read Only Memory is a fancy term for: you can’t edit it, you only can read it) it’s a published book. It’s already got a binder, cover art, and liner notes, and is released into the market... the only thing you can do is create a Second Edition, and remove the First Edition from memory. Here's info on this process:

How you do this is you use the “Library Import” function.
This is a routine that copies some or all of the Library data to the User Bank - WITHOUT overwriting what is already in the User Bank.
This allows you assemble data from multiple File and combine them into one Bank.

It not only copies the data from the ROM Library, importantly, it takes any Element that was referencing a ROM Library Waveform location, and points it to the copy it made in the User Bank. (It takes the Waveform data from Flash ROM and places it in the User Waveform Bank.

Once you have assembled all the data you want from your various installed Library into one User Bank... you can SAVE AS... Library File .X8L
Remember the LIBRARY File is told to repoint the User Waveforms to the lowest numbered empty slot when it is loaded.

You SAVE AS a new Library File
Now you can manual DELETE the First (installed) Edition, and install your newly updated Second Edition.

Thank You!

I like one library file better than 100 points of wave data in folder. It is more comfortable

BTW I don't found on MODX how to create multisamples for (AWM2) Normal voice.
There is I not see sample zone anywere

One way I make Motif XF(X0W) in Awave Studio and install it

Thank You!

I like one library file better than 100 points of wave data in folder. It is more comfortable

But it is not at all about what you “like better” lol... when working on creating new sounds, it exists as data in the User Waveform Folder where you can *manage* and edit it; when you install data to ROM (Library) it is available only to be Read (accessed) only, you cannot manage it, nor can you edit it. What’s “like” got to do with it ?

BTW I don't found on MODX how to create multisamples for (AWM2) Normal voice.
There is I not see sample zone anywere

The MODX does not sample, and it has no “Voices”.
You can load a .wav into a Waveform directly as you create a playable entity. It is loaded via the Element and the data is stored in the User Bank. (Waveform Folder).

On an AWM2 Part
Press [EDIT] navigate to an ELEM screen
Tap “Osc/Tune” - this is where in a sampled-based Part a Waveform is selected. You will see what Bank (Preset, User or Library) it comes from... if it is a User Waveform you can edit it.
You will also see a box labeled - “New Waveform”
This allows you to Load a .wav File to a new Waveform from your USB stick.

A Waveform can contain 128 stereo samples or 256 mono samples.
You can have a maximum of 2,048 Waveforms in your User Bank (over 8,190 individual sample wav) at maximum
Each .wav file can be placed in what is called a KeyBank... which is simply the Note Range, and the Velocity Range, etc. for this particular bit of audio.

One way I make Motif XF(X0W) in Awave Studio and install it

The MODX can load Motif XS/XF Waveform Files. A .X0W is a Motif XS “All Waveform” file. A .X3W is a Motif XF “All Waveform’ file. Both can be loaded directly to the MODX. Their contents will be available on the “Elem” > “Osc/Tune” screen.
Motif XS/XF Waveform data is already organized as KeyBanks and are loaded/converted to MODX Waveforms in the load process.