The subject line says all:
Manage to get a bug to be in the debugger (by, for example, trying to populate a non existing Row of a Listbox to get an OutOfRangeException) and run the project:
You will get a red bug at the left of the offending line. Usually, with previous versions (not Xojo 2018r3), I get a text clue in the Code Editor (the Debugger in that case) bottom.
Not with Xojo 2018r3. And you ?