Display possible block locations?

I am in customize site, any level. I want to select some content, the logo, or text or whatever. I know where I want to put it, but I'm restricted to clicking and holding and mousing around hoping I see a container location pop up before I go to far and get a nasty message telling me I'm supposed to put my content in a valid location.

Oh, it's very clever to highlight the possible locations that I can't put it in with different colors -- if I'm customizing a page or gallery, and i mouse over a whole site location, it pops up in red for me. It's of course good that i be informed I can't drop my content there. But what I'm seeing is an otherwise blank slate that has very specific places I'm allowed to drop my content at, but no visual clue where those are until I start mousing around, and even then, sometimes hard to see, hidden under the content image that I'm dragging around with the mouse.

What i really want is a mode or a command to display all the possible locations for the content I've selected; and, optionally some other color indicating the locations where I can't drop it.

We have that on the entire site page, why not the others, too?

If the answer is because the locations allowed for Homepage, all folders, all galleries and just this page are different depending on the theme -- well then, of course I want to see that, even more so.