[XODIDOX]

Personally I would make the list shorter. I understand the purpose of the list is to save the user time (button-clicks). But a long list does the opposite, it takes many clicks to get to the one you want (or even to see what is available).

I would cut it to 20 or less. Use the following criteria:
a) how common is it
b) how much button presses does it save to include it in the system-defined list versus entering manually

for example
Extended Edition - a) Very common. b) has lots of letters so takes a long time to type via on-screen keyboard. Keep it.
VHS - a) Very uncommon. b) Only 3 letters so can be typed pretty quickly. Lose it

This is a good idea. My suggestion would be to have this file, editable, somewhere in the user directory. This way one could customize it to their needs.

I have thousands of movies. Once this feature is implemented officially I will need to go through all of them, to properly identify versions. My main usage will be for 4K/1080 versions. Others might have lots of Criterion versions, others different needs. If the list could be customizable, it would make it easier for big libraries to be adapted.

I am not saying to eliminate the list. It makes sense for new users and, generally, to give an idea of the possibilities. But if it could be customized, it would be nice. If this is too complex, ignore the suggestion. I don't want to overcomplicate things (the suggestion goes the opposite way, from an end-user point of view).

I can add a "delete" context menu item in Library->Movies->Versions, so you can delete a version that you won't use.