Can I make a collection with mods that are not in nexus?

[crunkops]

As the title says, can I make a collection with mods that are not in nexus and upload it to nexus? will players be able to download the mods that are not in nexus?

[RomanR]

No, of course not. Even if by some miracle you get all permissions from authors of these mods and prove it, no one will host your collection containing files from uknown source or linking to them for security reasons. 

[LenaWolfBravil]

I am not sure that's true. You can have files from external sources in your collection. Isn't it what the OP is asking about?

[showler]

Unclear.  You can certainly have external sources in your Collection (though it usually ends up requiring a manual download and installation, I think, unless the site has an API that Vortex can access), but the OP is unclear about whether they mean some non-Nexus sources or ALL non-Nexus sources.

[Pickysaurus]

This may answer the OPs question

https://modding.wiki/en/nexusmods/collections/create/add-external-mods