> The gui doesn't seem to have a way to open an executable.
Activate the "Load Executable" button in the toolbar.
> Using "Open Source Code" produces a file dialog that doesn't seem to have a way to paste paths.
Paste in the location bar or in the file name field, or access the context menu of the location bar and activate the "Paste" menu entry.
> Passing the test exe at the command line (kdbg ./test) open up an editor at start.S but still doesn't seem to have a way to run the exe.
Activate the "Run" button in the toolbar.
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Verdict: too fucking rushed that he doesn't use common sense and tries the obvious things.