DEBUG and RELEASE should out of the box be enabled and set to RELEASE, so everybody will be happy again...
Setting to release is not an advantage. Most people will have plenty of debug builds / debug-run before they compile a release.
But buildmodes could have settings:
Name for run menu entry: Creates a run menu entry "Build <mode-name>" (so you can build release, via: run > build release)
The run button would still compile the current build mode, by default "debug". Because running a none debug build in the IDE (in the debugger) is really pointless.
Only needs a person willing to work on it.
EDIT:
Adding build mode to the output directury would maybe help too. If the files are in lib/debug/x86-64/ most people will realize.
If you set the exe to go into the project folder then maybe it should be named project1-debug.exe
(Or whatever the buildmode name is)
<< End EDIT
ideally show the mode in the program (form) caption. 
Issue of its own.
Though at this stage, I would say that adding another checkbox, for what goes into the caption, is the wrong way.
If someone wants to give it a go, I think the IDE caption should be build-able from macros:
$(ProjecName) - $(BuildMode) in folder $(ProjectDir)
just my 2 cents
AND by the way I tried this DEFAULT checkbox a couple of times, but on my system nothing changes ...
I haven't tested it, but sounds like it could be a bug.
I guess you have to leave the dialog with "ok" when this is checked. But not sure.