With the mouse pointer in the thumbnail window, Control + mouse wheel enables thumbnails to be enlarged from the original size and then decreased back to their original size - in VP12 & 13 anyway.

VP doesn't remember the adjusted size on closing and reopening the program, so you'll need to reset the size each time you open VP.

Dexcon

That only works in the Explorer but not in the Project Media tab.

What I should have written was:

NO, for Project Media.

YES, for Vegas Explorer.

I was also going to add Media Manager as an option, but decided that explaining that would be far too long winded, and that it was better to have less description than more.

G

For anyone reading this in 2023 or later, Ctrl + mouse scroll works in the Project Media view as well. No idea how many versions this has been the case, but in over two decades of using Vegas, this is the first time I have ever needed to expand the thumbnails! Disappointingly, the thumbnail size still does not persist as a global Vegas setting, nor as a per project setting.

@Ian_S  ... thank you for pointing that out ... it's good to know.

Yes, it's always been a pity that the thumbnail size isn't memorised any any way.

I actually spent five minutes going through every option in the Project Media (and Explorer) tab - I was convinced I'd seen a slider that changed the size of thumbnails. I must have been thinking of a different NLE!
In this age of high DPI and ultrawide monitors, I would have thought this a very useful feature - that being said, this was the first time I needed it (to read the text on some title plate graphics). As I plough into my myopic sixties, no doubt that need will grow :-)

Hah!! This works on my Logitech Wireless MX Master 3:

Rubbing with my Thumb gets Bigger and then Small Thumbnails. It's the same procedure as getting ZOOM-in and ZOOM-out on the Main T/L!

Rubbing with my Thumb gets Bigger and then Small Thumbnails

It's not the same here. With scrolling the LH thumb-wheel (with or without CTRL), I get L-R scrolling through the thumbnail.

It's not the same here. 

@Dexcon - Really? Well, we’ll look into that. For me it’s immediately responsive. Dang!

@Dexcon - Just did a Demo just for you: https://www.dropbox.com/scl/fi/gedc9l0z9ler02qshqs5w/Demo-of-using-Logi-Thumbwheel-for-Zoom-Thumbnails-1a.mp4?rlkey=gicfjfbjn5lelgs18hgylqnge&dl=0

@Grazie  ... many thanks. I discovered the problem. Since having just installed a new C drive and reinstalling everything, I needed to add Vegas Pro to M3's 'Apps' and then assign 'zoom in/out' as the 'Action' for the horizontal wheel. That wheel is now zooming in/out on both VP21's Project Media and Explorer windows.

Thankfully, I don't have to do a reinstall very often (it was about every 6 months back in XP days) because there's always a few things that I've missed/overlooked. Even this morning, I had to swap the new NVMe back to the original because I'd forgotten to copy VP's custom Render Templates in C:\User\xxxxx\AppData\Roaming\Vegas.

Thanks again.