As with any thing that would appear in the Context menu, in order to see it in the Shortcuts list, the state of the drawing must be such that it would show in the context menu. Select a component (single click) and then open Window>Preferences>Shortcuts. in the Filter line, type Flip and you should see the three Flip options. Set the shortcuts as desired. Click OK.
After you've set those, either open the component for editing and select the geometry or select two components and repeat the process.
I use F2, F3 and F4 for Flip along Component's Red, Green and Blue and Shit+F2, Shift+F3 and Shift+F4 for Flip along Red Direction, etc.