Layout: Folder View

When I hover over a desktop icon, there is a +/- toggle on the upper left. It doesn't seem to do anything. What is it?

That icon is to toggle selection (same as ctrl+click, but allows mouse-only selection). You should see similar behavior in Dolphin.

Ahhh. Okay.

I've been switching between Desktop Layouts between Folder View and Desktop Containment (I'm testing/learning on a VM in preparation). And in Folder View I no longer see the +/- when I hover over the desktop icons, only the up arrow to expand is there.

I see in Dolphin, Settings > General > "Show Selection Markers". Do Dolphin settings affect the Plasma desktop Folder Layout (like Gnome based desktops)?
I did have this turned off. I turned it back on and even logged out and in to see if it impacted the Desktop, but it seems I've somehow lost the +/-. HHHmmm....

Something else to try (just to help nail down where the problem may be) is to add a Folder View widget to the desktop (when the desktop layout is either Desktop or Folder View) and see if that Folder View widget shows the +/-