Highlighting in Read or Full Screen mode
How do I highlight test in Reading Mode or Full Screen mode? As far as I see, the highlighting tool (and probably many other tools) switch off in these screen modes and even the pin button does not change this.
The skeptic commented
open the Preferences dialog box (Edit > Preferences), and under General, select the Use Single-Key Accelerators To Access Tools option.
After making changes in preferences you can use Shift+U key for highlighting even in full screen mode.
I have the same problem, it would be great for this feature to work!