Closing Blocks Palette

I have a "popup toolbar" that I created almost 20 years ago that... I press a button on the mouse/gamepad and a toolbar appears in the center of the screen, I select a command, the toolbar disappears, and the command is issued.
I'm spoiled now...
I want my new blocks pallet to do the same thing.
I want to type "I", enter, blocks palette opens, I select a block, and the palette disappears.

So...
Is there a new command that only closes the palette? I can't find one.
Is there a rabbit hole I can be led down on how to accomplish such a feat of greatness?
Thinking I might have to work on my reactor skills, but dunno.