use the pen tool to add to an existing mask

Thank you for your response, but I have no idea what you're talking about. I need to use the Pen tool to ad to analredy exsisting mask.

If you look at this image here, you'll see a black triangle on the right side of the image and basically the idea is I would use the Pental to add a shape just like that to the already existing mask. No matter which I use path or shape on the Pental. It doesn't add anything to the mask and sometimes it doesn't even add anything.

Also, just for your information, maybe it's not difficult for you, but I've been using Photoshop for years and what you suggested is objectively and demonstrably far more difficult than just using the Pental and clicking the corners or angles of the mask you want to makemaybe it's not difficult for you, but I've been using Photoshop for years and. Either way, not trying to be a smart ass. I appreciate your help.