For this answer (now deleted), where the OP tried to add additional information to their question, the "convert to edit" option has been disabled in the moderator queue:
However, when I open the mod menu of the post, the option is enabled:
How is this possible?
EDIT: the suggested duplicate tells that there's an algorithm switching the button on or off depending on certain conditions; the author of that question thinks a comment on the answer might disable the button (but has subsequently struck through that part of the text). If this is true, I'd like the algorithm to be changed (so this becomes a feature-request ...); many times, flaggers will leave a comment asking the author to edit the information into their question. There's an AutoReviewComment doing that, and maybe even one generated by the Low Quality Posts review queue (not sure about that, and it's hard to find testing material).