What kind of software can I use to design LEGO MOCs? I hear the LDD is not so good to use so is there alternative software I can use?
In the comments you asked,
...do you know if it is possible also to work in stud.io with other 3d-files or only with bricks that are pre-integrated? So if i would have designed new bricks could i use them too?...
Looks like Brinklink also offers a tweak program to make custom bricks called PartDesigner, that's able to export right into Stud.io. I've never used it, but it might be promising to you.