I found that when working with python scripts, I have to manually save my files before debug or execute. This is a bit annoying because when I forget to save the file, an old version is launched giving unexpected results. It would be nice to have an option (or a default in python) that would save the file on the moment I press any of those buttons (or at least a warning telling that an old version of the file will be launched) For some background on this, and some workarounds, there is a thread in the forum here (https://forum.kde.org/viewtopic.php?f=218&t=138642)
I confirm the problem with current 5.2.2 AppImage version. C++ programs can be automatically built with saved sources when ran or debugged. It should be the same for python project with custom build system (without the build step, obviously). (I put the status as CONFIRMED. Is it allowed or reserved for the developers confirming the bug?)
*** Bug 413674 has been marked as a duplicate of this bug. ***
I have found another workaround. In the "External Scripts" panel create a script. Add the command "%f". In "Save mode" option set "Save Active Document". Then assign a shortcut for the script. Then use that shortcut instead of Execute and Save buttons/shortcuts. See the video for details: https://youtu.be/nQ5Iqr8-Ftc
As I see it, the solution from the UI perspective is to add a similar "Save mode" option to the Launch Configurations window.