I would like to highlight endnote references in the body of the text to make proof reading easier. What I mean by this is that I would like the little number that references the endnote from the main body text to be highlighted, e.g. with a yellow background.
Open Styles sidebar (F11), and navigate to Character Styles (second button with “A”). Find Endnote Anchor character style, right-click it, and select Modify.... On Highlighting tab, select desired color.
The exact character style used in your document might be named differently; use Tools→Footnotes and Endnotes... (Endnotes tab) to find out actual text area character style name.
Ah, I hadn’t spotted that there are predefined character styles as well as paragraph style. Your suggestion worked perfectly in a new Writer document, thanks. Unfortunately it doesn’t work in a document converted from Word .docx, it seems that Word and Writer handle endnotes very differently.