Most keyboard commands are displayed in the menus as accelerator keys. The defaults follow KDE standard when applicable. You can define your prefered key bindings using the KDE standard key configuration dialog available from the menu Options/Keys.
Note also that you can reach most menu commands with a couple of key presses, e.g. to show the Help/About is done by Alt-h a. You can also use cursor keys to move around in menus. Here is a list of invisible bindings (these are not configurable):
SPACE moves down then to top of next page similar to Advance button.
Cursor keys scroll in obvious way. With Control-modifier they use a very small step size for accurate control.
Home scrolls to top of page.
End scrolls to bottom of page.