Is there a way to add your own 3D models into the game?

Okay so I created a mod and enabled it. However, I created a simple capsole model in the mod and created it under parts. I enabled the mod, but can't see the model installed at all when I go into the build editor to make a rocket. Any help would be nice!

@PointBreak yep its updated to 2019 which broke alot of stuff

@MarioG Oh ok. Just to clarify is it because the game is made in newer Unity versions, or because there's a lot more mod tools? I'm new to modding, and was also looking into adding stuff (if I have the patience for that lol).

@PointBreak @Ev3rlast that tutorial should work but keep in mind it is kinda old, the mod tools have changed alot but it should still work

IIRC, MarioG made a tutorial.
Found it.

Nobody adds their own rocket models into the game. People take the time to sit down and build them from scratch.

Maybe XML?