In Writer the Tools > Customize > Keyboard > Functions > Category > Format > Function includes both the Highlighting and the Highlight fill functions.
What is the difference between them? A regular user can not be expected to see the difference based on those labels. A different label could be useful. I don't have any specific suggestion for an alternative label, because I don't know what the difference is either.
Additionally, as it was reported, the Highlighting shortcut does not work https://bugs.documentfoundation.org/show_bug.cgi?id=34804, which makes the situation even more confusing for a regular user.
If you want to know the difference between such entries, you should try adding them as buttons into your toolbar and then you will see its behaviour ( Tools > Customize > Toolbars ).
Highlighting is the highlighting split button in the toolbar and Highlight Fill is to activate the cursor highlight fill mode.
Migrating Whiteboard tags to Keywords: (needAdvice)
'needsConfirmationAdvice' is only used for unconfirmed bugs. Removing it from this bug.