So if I understand you correctly, you have a Metadata Template where you type =11= into the Persons Shown field, and then you use the {persons} variable elsewhere to insert that name in other places? If so, you could use Hot Codes to also insert an IG handle. If your Code Replacement sheet had a section like this...
// Code Replacement file with Hot Codes for Photo Mechanic
// Enter the variables you will be looking for strings in
//== {persons}
// Name your hotcodes here
//## ighandle
#11 Paul Meier @paulmeier1
#27 Mick Orlosky @redfishingboat
#99 Wayne Gretzky @waynegretzky
//??
You could apply a Metadata Template with a caption of "This is a photo of {persons} [ighandle]"
For a photo where "#11 Paul Meier" is in Persons Shown, then
[ighandle] will be replaced with
@paulmeier1, but the same template applied to a photo where "#99 Wayne Gretzky" is in Persons Shown, then
[ighandle] would be replaced with
@waynegretzky etc. And if the Persons Shown field is empty, then {persons} & [ighandle] would both be replaced with nothing.
Is this closer to what you're looking for? (I attached the file also)
-Mick
More about Hot Codes is here:
https://camerabits.freshdesk.com/support/solutions/articles/48000358684-hot-codes