Just a note in agreement that the black plastic pin in the triangular piece is seated very tightly. IMO there's a high degree of certainty that you'll break the pin - as I did mine. Fortunately, the window gaskets nicely hold the triangular piece in place even with its broken pin.

The rest of the story is that I was trying to remove the whole entire mirror housing of my '93 245 so as to paint it on my work bench. My mirror is power operated. Once I removed the triangular piece I saw no means of detaching the mirror assembly so I proceeded to seek a way to detach the whole mirror and mirror housing from behind the mirror and inside the housing. Once I removed the mirror (see reference below) I found that the wiring for the mirror motors terminated deep inside the car and were too difficult to exactly locate and disconnect considering that my goal was simply to paint the mirror housings. I reassembled things, masked around the mirror housings, and painted them in place with good results.

Instructions for removing the POWER mirror from the mirror housing for a '93 240 can be found in my comments on the "Robert DIY" YouTube channel. His excellent post is entitled " Door mirror replacement, manual, Volvo 740, 940, 960, 240 etc."

These pictures have been quite helpful. Thank you.

I just replaced the driver side mirror on my 240. However, it is difficult for me to put back the triangular plastic trim piece. If anyone knows the trick to put it back in, please let me know. (Should I remove the inside door panel first? If so, how?). I ended up breaking the plastic tab on the trim piece.

Thank you.