Why can't I edit my signature in my draft composer?
If you can't change your signature while drafting an email, it's likely because your signature is in the HTML format. This format can't be altered in the draft composer.
You can toggle between the HTML and Rich text formats by navigating to Settings > Signatures > Edit. Then, look for the option at the bottom of the Content field.
Be aware that if you switch from HTML to Rich Text, you might encounter some unexpected visual changes, especially if your signature's HTML code is too complex for Rich text.