How do I remove ALL highlights - please
Delete all Notes with highlighting. Select "Highlights" in the Notes Sidebar filter and use mass selection to delete them i.e. select one then Shift-click the last one and use "Delete selected notes" at the bottom of the right column.
In the Notes Tool, use the Type filter on the left to select just your highlights.
Then click the top one to select it, followed by Ctrl/Cmd-A to select all of them
You will then see the option to Delete Selected Notes
Please be sure you want to do this before proceeding!!
This seems like a pretty drastic action. Perhaps you want to just turn them off in the visual filter menu (three circles icon on the resource panel)?