Currently, it's not possible to set "Maximize/restore" or "Keep above" toggle in "Inner Window, Titlebar and Frame Actions" for left/middle/right click. They can only be set for a mouse wheel where mouse wheel up maximizes and mouse wheel down minimizes. In the case of Keep above, the mouse wheel can only be set to "Keep above/below" 3-way toggle which is where I think having the option to use a mouse click toggle instead would work great as it would prevent accidentally setting "Keep below" when accidentally scrolling down twice. I initially wanted to also request "Double click" actions in a separate feature request (specifically, I wanted to be able to maximize with a double click as that's how I used to have the AltDrag app on Windows set up) but after looking through the bug tracker I found that it's unlikely this would be accepted: https://bugs.kde.org/show_bug.cgi?id=43583