@ parel : cool pedagogic video !

Very mysterious : today that works as excepted! So more easy !

And better (very curious again): select faces "trimed" Inset don't works

but if you call Details & select "4 faces" then call Inset that works fine!

So a groove is made with only one click after the trim with the Inset "0"! (curves killed)
No need to select one by one as the image!

PS Works only for ortogonal path ! Better than nothing! :)