You can add all such objects to a family. Then use "Family on created" event.
Thanks for this suggestion. Was able to get the layout to work after putting all the various "box" objects into a single family.
This brings up another question about families or containers (or maybe neither of these)...
If I want to reposition a bunch of objects as a group, for example, to create a transition where all objects (cards, pieces, dice, etc) on a game board animate off the board in a defined direction, is there some way to define/reference this grouping, using either families or containers (or something else)?
I'd like to apply animation to the objects as a group, rather than having to pick through the various object types and instances.