@baris Indeed, I was logged with admin account. I tried with a regular user and it works correctly. The "Upload Image" button does not show and uploading with CTRL+V gives me the following error:
Thanks for clarifying and sorry for the misunderstanding.
Thanks @julian! The code is a bit daunting and I don't want to risk breaking anything at the moment. Is there any other way for me to change the og:image meta property? I tried adjusting my logo size but, that just made my logo smaller because of NodeBB's resizing in the header.