Not necessarily. If you go to bugs.kde.org, you can just describe the bug in your own words: what you do to trigger the bug, the expected result, what really happens, etc.
Of course it is best if the bug is reproducible, i.e. that you discovered that every time you do x, y and z, a crash happens, for example. Like that, devs can confirm that it is indeed a bug of the software and not something that happens only due to some special configuration or hardware problem.