The compose / editing system is VERY limited.

As I have mentioned previously, when writing longer emails, I need to use MS Word then copy/paste back to Mailbird. I do this because: to change a font or font size in part of the email requires a two-step process IF the rest of the email was already in the required font (i.e. for the whole email .... first change to a different font and then change back to the required font) The alternative is to change the font / size of ALL the "wrong" words and sections individually, one at a a time!
More importantly, the mailbird compose function does not allow for direct drag / drop of text. I have to highlight the text, then copy it, then drop and paste it in the new location and then go back and delete that text from the original location.