Trigger action for Hexes on the map to make AOE appear

What I am looking for is a way to trigger a hex to display a 1 range AOE when occupied by a Combat unit in the game. Combat unit is defined in GAME piece prototype Definitions.
I am currently using markers to do similar but, they are giving me a little trouble by over stacking a unit that begins the game in the same Hex, I have the do not stack trait on these markers and it is not all of them just Random hexes with these conditions, IE existing with any other counter in the same hex.
Any Ideas?

How, currently, do you determine which of the peripheral hexes form the AOE ?

Idea: make your existing marker pieces invisible (remove the image that forms the piece).
Instead, put a single hex AOE trait on that piece. Make the AOE always display, or have the marker piece remain always in place and have a command to turn it on or off as required.

Mark, you are describing exactly what I currently have in the module.
I put a marker counter on the map that has the trait Don’t stack, AOE 1 hex and special select to move it.That was what you saw up thread ( a small square on top of a counter on the mapboard.) That is what I am trying to get rid of. I would prefer to not have any AOE active on the hex until a combat unit is placed in the hex which is using hex numbering. I thought that since the AOE is only active when a combat unit is in the hex it might solve this weird marker on a unit issue. and be pretty fancy.
I.E. the 1 hex AOE is off until a combat unit is placed in the hex, if I could build a list of hex numbers with this trait “AOE=1 hex radius” that would be better and cleaner than a marker sitting on the board.