Many games will have multiple exes, whether its for different graphics apis (i.e. one dx9, one d11; one dx11, one dx12; one opengl, one vulkan etc.), a launcher and the game proper, or a collection containing multiple games, and so on. It would be nice to be able to setup games like this to have a selection when you press play (like many steam games, and I believe some GOG games, do), rather than having to pick one or the other, or make extra game entries to work around it.
On a similar note, it would nice to have the option for non-manually added games (so GOG games or games imported from an integration) to modify the executable used, for cases where modding has you use a different exe (for example, a mod launcher, texmod, injector etc.)
And I imagine this is already something being worked on (given it was in previous GOG Galaxy versions), but a command line option tool would also be very helpful.

Yeah this one is a biggie for me too.

We have games like Euro Truck SImulator 2, where the single and multiplayer parts of the game are different executables. Honestly I wouldnt mind also an option for adding an "Unknown game", where you can edit the cover and name so you can handle cases like this, or add games that are not (and might never be) in the database.

+1

This please!

I'd like to show my support for this one. I've Resident Evil 3 Nemesis for PC and the main game and Operation: Mad Jackal are two different exes.

Third party mod launcher support in GOG Galaxy 2.0, is an essential for TES Morrowind, and Oblivion, and Fallout 3, and Fallout New Vegas.
Without the mod launchers, the game extensions can't be applied or used, and far too many mods for those games, have those extensions as mandatory essential.

Just chiming in to agree that this is a must-have.

You can't really play Fallout 3 without Script Extender...

I completely agree, this is especially important for games like DOSBox, which can have setup programs and source ports.

Yes, this is very important. I've been working on adding old emulated games to galaxy, but many older games use multiple discs (and thus, multiple .bat files) and galaxy 2.0 currently has no way to handle those.

Agreed. It seems the data from the .info file for GOG games is ignored. I had previously edited them to add more run tasks to run different flavors of the game. The .info file should be available for every game no matter the collection and support adding new playTask entries.