If you have customized your keyboard layout to have the plus ( + ) key be present for both shifted and unshifted modes, then the shifted mode will not result in the "add" function occurring in kcalc despite it displaying a + character in kate regardless of whether you are holding the shift key or not. To clarify, I use the Colemak keyboard layout and have simply modified the file /usr/share/X11/xkb/symbols/us so that, under "Colemak", the line for "key <AE12>" lists the following instead: key <AE12> { [ plus, plus, multiply, division ] }; For reference, I then also modify the backslash key so that it instead works as "equal" and shift+backspace works as "backslash"; this is all because one is not able to use the "equal" ( = ) key for the "plus" function as I described in the following suggestion: https://bugs.kde.org/show_bug.cgi?id=461485 STEPS TO REPRODUCE 1. edit and overwrite the file "/usr/share/X11/xkb/symbols/us" and replace the 'equal' function for "key <AE12>" with the 'add' function (without quotes) 2. log out and log back in 3. confirm in kate that pressing the equal ( = ) key without holding shift sends the 'plus' character, and that holding shift while pressing the equal ( = ) key also sends the 'plus' character 4. open kcalc and click the number 1 with your mouse 5. press the equal ( = ) key on your keyboard 6. click the number 2 with your mouse 7. press the enter key; it should now display a value of "3" 8. click "AC" with your mouse and then press the number 1 with your mouse 9. hold down shift and press the equal ( = ) key on your keyboard 10. click the number 2 with your mouse OBSERVED RESULT kcalc is now displaying a value of "12"; it would seem that holding shift while pressing the equal ( = ) key in this scenario did nothing EXPECTED RESULT kcalc should have instead did the addition equation of 1 + 2 like it did when you were not holding shift SOFTWARE/OS VERSIONS Linux/KDE Plasma: Kubuntu 22.10 KDE Plasma Version: 5.25.5 KDE Frameworks Version: 5.98.0 Qt Version: 5.15.6 ADDITIONAL INFORMATION When modifying the file "/usr/share/X11/xkb/symbols/us" it does not matter if you use the 'plus' function or the 'KP_Add' function as both seem to result in the exact same issue, and this issue occurs even if you have the primary unshifted function as 'KP_Add' and the shifted function as 'plus'