Highlighting in Word - problem

Through numerous versions of Word, I've never known it to act as you describe your desired behavior.

Note "highlighting" in word is marking text with a background highlight color. It is different from selecting text which is entirely temporary.

What is persistent is the highlighting color. When I change from the default yellow to green, the color that will next be applied with the highlighting tool will be green. This persistence is at least while that document is open and may be while Word remains open. (I have not checked.)

If you select some text, then click the highlight tool, it will be a one-time action - the tool won't remain active.

If you select some text, then double-click the highlight tool, the tool will remain active until you click it again or you press Esc.

If you don't select text, i.e. you see the blinking insertion bar, then click the highlight tool, it will remain active until you click it again or press Esc.

Hello!

Thank you for your comment!

This is exactly what surprises me!!

I see blinking insertion bar, then I click the highlight tool, then I highlight something, BUT the tool does not remain active!!

I have two guesses -

1) it can be somehow related with autosave. Because before this strange changes occurred, the highlight tool  was switching off each time I pressed Ctrl+S to save the document.

2) I installed the plugin from Mendeley Desctop to set references in the texts that I write in the Ms Word.

Hello!

Thank you for your comment!

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2) I installed the plugin from Mendeley Desctop to set references in the texts that I write in the Ms Word.

What happens if you start Word in Safe mode or without Add-Ins?