Yeah, i should be more clear; the only way to 'revive' destroyed units while running/testing a scenario in the mission editor is to set 'revive' conditions. Referencing a region is a very simple way of doing it. Also referencing a trigger gives you a sort of ON/OFF switch for the revive zone. I find this useful for ammunition/ lethality/ matchup testing where you want to test repeatedly without needing to exit and reload the scenario a hundred times.
Ill attach a video showing how to setup a triggered revive zone, this may or may not be relevant to the OP's particular (and unspecified) ne