Try this....

• On the 'Tools' menu, click 'Customise'
• A small window appears which should have a button labelled 'Keyboard' toward the bottom right-hand corner - click the button - another window opens
• On the left of this new window should be a list of your menu options (File, Edit, View, etc); click on 'Format', and the relevant menu choices should appear in another list
• Scroll down this second listuntil you find 'ChangeCase'; click on this and the current shortcut keys assigned to this command should appear in the window under where it says 'Current keys'.
• You can at this point change which keys are assigned if you want- if you do, click the 'Assign' button to confirm the choice you make.

On my work laptop 'Change Case' has Shift + F3 assigned as shortcut keys, so you might try that. Still have to highlight text, and each time you press keys it changes appearance of text.

See how that goes.....