Holy cow I think I figured it out. Accidentally 
So I have a repeating group with group inside each cell, and a button inside each of those.
Inside the group I also have an icon (but I’m guessing you can use other elements like your box shape). This is what I want to display on only one button I’ve hovered in the RG.
Here you can see the basic set up:
Attached to my RG I have a workflow, done via the Workflow section. Click to add a new event, and select “Do when a condition is true”. In that you write an express when “RG_X is hovered” like so:
Then add an action, “set state” with a custom yes/no state, in this case I did “tag-hover”
And then… on the icon itself, you can add a conditional that says when your hover state is true and the single group itself is hovered, then set it to visible:
Now, you can see in preview when I hover on that element, only one of the icons is showing!! And it’s clickable/hoverable in its own right, hence I’ve made it red on hover as it’s a delete action.
I LOVE BUBBLE! hope this helps. I think I’ll be able to use this for other instances where I want an overflow menu icon to show up on hover for a particular card/group, and then show a floating menu that pops up. Cheers.