Open the Clipboard Master list (e.g. with Win+V), press Cursor left to show the list with the clipboards.
Now click with the right mouse button on a clipboard or press Alt + F9 within a selected clipboard and then select "New". You can create the new clipboard below or within the selected clipboard.
Open the tray icon menu (right click at the tray icon) -> Settings -> New -> New clipboard
Open Clipboard Master, select a clipboard and press Delete. You can also click on a clipboard with the right mouse button and select "Delete".