To change the shortcut key arrangements used by KPlayer select SettingsConfigure Shortcuts.... This will open a dialog box as shown below.

Shortcut configuration dialog

If you change the key bindings, make sure not to duplicate an existing shortcut and also not to use the Shift key for your new shortcuts, because the Shift key has a special function in KPlayer.

Use the filter bar to search through the list to find the action for which you want to add or change the shortcut keys and select it by left clicking the name in the Action or the cell in the Shortcut column to change the primary key. Click on the cell in the Alternate row to change this shortcut. You will then be able to change the shortcut by clicking the None button.

Press the key or key combination you want to act as the shortcut. Clicking the little black icon with a white cross in it clears the shortcut.