No.
There's quite a lot of things that can't be done in a Steam mod.
Outside of Steam there's the TSLPatcher to circumvent issues.
However, you can apply most mods to your steam version of the game, just remember to point the TSLPatcher to your Steam workshop TSLRCM folder if you use it.

A question & a spoiler regarding the Atris mod:

Why bother creating such a mod if you can't really make good use of her as a companion potentially for more than just one mere planet versus at least 2 or 3 ? This was why the "Handmaiden" character was created.

Your character will not have any real interaction with Atris beyond basic storyline arcs until you get to the last few parts of the game - she's not meant to be a companion.

I agree that the game is incomplete, & was rushed into gameplay - but that was why the restored content mod was released.

Furthermore, there will be specific mods that are not Steam compatiable - one has to download them & install them in the old fashioned manner - unzip, & install in the specific directory.

SHe was originally not going to be a companion for that long anyway.

Originally posted by ricochet_29:

A question & a spoiler regarding the Atris mod:

Why bother creating such a mod if you can't really make good use of her as a companion potentially for more than just one mere planet versus at least 2 or 3 ? This was why the "Handmaiden" character was created.

Your character will not have any real interaction with Atris beyond basic storyline arcs until you get to the last few parts of the game - she's not meant to be a companion.

I agree that the game is incomplete, & was rushed into gameplay - but that was why the restored content mod was released.

Furthermore, there will be specific mods that are not Steam compatiable - one has to download them & install them in the old fashioned manner - unzip, & install in the specific directory.

Atris was going to join you after you chose to spare her late game. She would have aided you in the Nihilius battle but that was cut out.