I've been working on a collab mod, and there's some custom content I made for it that requires extra files (models, textures, scripts, sound, quests and stuff).
I tried to use the Create Archive thing, but when I click on Pack Files nothing happens. The BSA with the same name of the ESP is 52KB big, a BSL file is 1KB big and a CKM file is 4MB big.
I need to make this mod an ESP and a BSA, because we take turns in this project.

Yeah, Create Archive seems to be a dead function. You will have to choose Upload Plugin and Archive to Steam (you can cancel at the last step if you don't actually want to send to Steam.) This will bring up the window to create your bsa, which will probably only have scripts in it. But you can drag your other files - the models, textures, and sound - from their respective folders into the window and then hit pack files. The bsl and ckm files are merely used for steam upload purposes. Your quest data is saved to the esp, and your scripts should be added automatically to the bsa (but you should double check the list).

When I try to use the upload to Steam function it gives me "Failed to share the mod file! Steam error 16".
What's that?

I tried the Workshop approach, and it doesn't work either.
Anyone?