Hey Mateusz, I think I understand what you’re asking. You want to be able to select a specific sub-mesh within an FBX? I have a screenshot of an FBX I’m using that has two separate sub-meshes. You can open it up by clicking the triangle icon next to the parent and then left click to select the one you want below:

You can also drag it out and use it as a completely separate piece if you’d like:

This is what we did with the Tower Defense assets. The props and vehicles were all essentially within two main FBX packs that we then took apart and used as needed. If you’re asking about something else let me know.