[Peter R]

If the text highlight was done using the highlighter tool, then you should be able to just select that annotation using the selection tool or the layer window, and then delete it. If you embedded annotations, you need to tap the three dots at the top right corner of the annotations editor, then Settings, then check "Allow editing of embedded PDF annotations", then you can select and delete the highlight. I would not recommend leaving that setting on all the time though, as it's known to cause instability with some PDFs.

Mike

Thank you very much! The Selection tool + Delete did it.
Excellent answer, much appreciated.

Peter