In RPs, I see floating objects that cant move and are always invincible which for some reason look like scouts.

Tho's are unused units, you can place them by going to units, Unknown, Unused.

They're easier to place in starforge. SCMDraft named them wierdly.

I still LOVE SCMdraft 2 though...

is there some special trigger or what not for these unused units

You cant create them, but you can remove them, kill em, make em poof, teleport em, know they're there, bring to location, etc

The only problem is that only units placeable in staredit can be created in game. All units can be preplaced (some crash the map though, or just don't show up).

Or explode, or stay there indefently

Or load a mod and make those units less crappy.

that's what it was, that reminds me of some things, you know how when you open up the Ai script at location, there's a lot of stuff in there is like "random seed, unknown seed, unknown, unused" what the hell is all that? how do i put it to use?

What are you talking about? There are no "seed" AIs.
Random suicide maybe that sends the comp's units to attack the nearest enemy.
Strategic suicide makes him pick any enemy and attack it regardless (iirc).

There is no unused AI script. Do you confuse that with unused upgrades? The last of those upgrades pretty much which isnt upgradeable ingaeme. Such as building armor, worker damage, spore damage, storm damage. Although many of those units have upgrade damage of 0, so nothing changes.

I suppose he means the AI scripts that were not availible in StarEdit.

An example is:

AI Nuke Here.