Cool, that will be usefull!
I'll try to define a requirment:
I think it will make sence to implement it as a behaviour, which can be added to basic object types (like families, sprites, tiled backgrounds, text etc.) Methods of the behaviour could be accesed through actions dialogue. Tag could be defiened in the behaviour properties or by an action.
In the actions menu there are 3 methods
1) Create object by tag
2) Set objects tag name
3) Pick objetc by tag (if it makes sence)
rexrainbow, thanks for your help