When there is a duplicate macro for launching apps, I get this small window:
If I type 'D', Edge app should be launched ('M' for emai appl), but I can't launch either app with M or E.
Duplicate Hotkey Trigger...
That's the Conflict Palette.
From the Keyboard Maestro Wiki:
In languages where characters change length when they are uppercased or lowercased (such as the German ß), Keyboard Maestro will not be able to handle either case selection for triggering the entry in the palette, so you will have to use the case as presented in the macro name.