When using REST importer (actually goes for any dialog), when user is trying to add parameter it is done as POP-UP, that is 4th layer counting original layout. I believe this level can be removed by inline editing on the table in layer 3, see the attached picture.

I guess I draw line at 4th level hehe

Also, currently in layer 3 the user is given editing choices in the table but once the focus is gone the value is restored to previous value (this is a bug)