How do I edit a poll?

A workaround is to delete and recreate the poll. Before you delete it, you can copy the /poll command by clicking the “...” menu on the poll and then “Details & More”, like so:

Once you’ve copied the text to recreate the poll, you can delete it from the same menu:

There is one thing that can be edited on a poll, and that's to toggle the "Add option" button on or off. This is also done via the same menu, then "Details & More":