If I’m editing YAML on the Mac Home Assistant app (not my browser), I can control + click and select “copy” from the menu, but the text never goes into the copy buffer.
Sometimes it’s handy to copy between the Mac app and Chrome to compare and share YAML code, but yes there are other ways to do this (multiple browser tabs, etc)
If editing an automation there is “Copy to clipboard” button at the bottom but that copies all the text not the selected text and it’s sort of strange to show “copy” from the pop-up menu if it doesn’t work.