Changing the type of a launch configuration from "Native Application" to "Script Application" in the Type column of the Launch Configuration listview doesn't immediately change the UI on the right to reflect the new type, nor does it remove the GDB child item, etc. Instead, one has to switch to another list item first, and only then the previous item has its type updated, so upon switching back you get the right UI.
there's even a patch for that under review: https://git.reviewboard.kde.org/r/101601/ *** This bug has been marked as a duplicate of bug 223158 ***