Insert and overwrite/overtype in Word Online, (aka Office 365 or now Microsoft 365).

There are a number of unresolved threads about being able to activate and de-activate this.

I noticed the most reliable way today while helping my daughter.

If you have a word or sentence selected, pressing insert key switches between the two modes. This isn't apparent until you move off whatever you have selected though :D.

Overtype mode is indicated on my browser by the cusor being a blue 1 char text selection highlight.

This is with the new Edge based on Chromium and in Chrome.