Is it possible to use baritone as gps, or add this feature? So that the baritone would not control the player, but only render the path and recalculate it from time to time.

you can use the command to path to the place/thing you want to go to, and the imidiatly do #pause. Then you can see the path but baritone won't walk it. ik this isn't a perfect solution, but you could use it temporarily.
You can use baritone's API to do this really fast and repeat it once a second for example.

What version are you on? Becouse I could test it(the API thing) but I only have a little experience with 1.12.2 modding...

Not possible and this feature is already suggested.