Not much more than video manuals, but the best available:

https://www.youtube.com/playlist?list=PLOgpPOaAOWW6QF59y9sfPeurEwAUevK7m

Mastering Montage Video Series:

https://yamahasynth.com/learn/montage/video-series-mastering-montage

This above link is a hub of information containing many links including:

Montage 101 series (6 videos)
Montage 201 series (3 videos)
Mastering series (15 video links provided)

Be aware that you can press the "Learn" option at the top of this forum which navigates you here:

https://yamahasynth.com/learn

Then press "Montage" under Topics, getting you here: https://yamahasynth.com/montage

There's 10 or so pages worth of content here. You can enter "Video" into the search here to pull out only those Montage-related resources that contain the word "video".

Doing this will lead you to more videos like the older Michael Tan series (9 videos):

https://yamahasynth.com/learn/montage/artist-michael-tans-montage-video-series
Actual videos indexed: https://www.youtube.com/watch?v=tAtlU9iVkLY

... and so on.

There are so many training videos available directly from Yamaha.

Additionally, you will want to go to the LEARN area. This is where you can review the wealth of data. The “Tech Talk” links will take to a video session where a particular topic is explored. There are tons of quick “Synth Tips” which can show you how to use a particular feature.

There are MONTAGE specific “Tech Talks”, and MODX specific “Tech Talks”; and most can refer to either product.
From the YamahaSynth HOME screen, click on LEARN, then on the right side you can narrow your search. Say you want to find info on the MONTAGE

LINK— YamahaSynth LEARN - MONTAGE

“Behind the Synth” are podcasts (SoundCloud).
And there are tons of tutorial articles that take you step-by-step through the product.

There is plenty of very recent content…videos, articles, discussions concerning the most recent firmware updates.

Hope that helps.

In addition to the training videos/options listed above, you can also google search &/or YouTube search for Montage "how to" videos.
Basically, if I want to know how to do something specific, such as add a custom .Wav file/sample to a PART (just as a quick example), I would just search "montage add custom wave file". The first video that shows at the top of my search in YouTube is:

https://www.youtube.com/watch?v=JXASiv3YfSE

Searching "montage how to add custom wave file to a PART" gave me similar results with that same video as the first one to check out...