Which Master is controlling which slide?

Hello again,

So I'm trying to figure out what to me is a very elusive answer to a simple question (sorry, just the long version today):

How can I tell which Master is controlling which slide? I need to know this because I'm importing a new slide with a Master that I want to use on all my existing slides - and delete the old Master.

But I've found that you can't delete a Master and associated layouts until all associated slides are either deleted or assigned another master.

Hovering over the old Master and layout thumbnails, I see that the Question layout is assigned to 2 slides -- BUT - it doesn't say which two slides! Since the program obviously already knows there are slides attached, it would be great if it could share the details somehow.

So I go looking...and sometimes, but often not finding, especially in longer presentations. That's the pain point, basically.

I've tried one suggestion of putting a big red rectangle on the whole master layout slide so I will visually see it, but it doesn't always show up on my main slides due to full image coverage. Sometimes I'll even see my Feedback layers with the red square, but I've no idea how to disassociate feedback layers from the Master slides - I didn't realize the two were connected...?

Yes, it's usually just me missing one slide, but it would be nice if, when you hovered over the Master thumbnails, it would tell you which slides were associated. 3DS Max has a feature like this in their material editor, that tells you which of your several hundred objects are associated with which materials. Something like that is what I think is needed. 

Thanks for any help you can provide. There is probably a simple fix, but maybe someone can benefit from my explanation in some way. See attached screenshot with old master and layout at the top, new master and layouts under.

alan

 ps. Upon posting, I discovered several other similar questions over the years, but no solid solutions. Yes, I think this might be a good a feature request! I'm sure it's no easy fix for programmers. Nothing ever is! lol.