Well, I have to admit that personally at this point: I do not care wheater wysiwyg or a helpful toolbar is the way to go. What I am trying to say is that the mobile text editor is nor a proper markdown editor nor is it wysiwig, IMHO it is way to basic and this (again IMHO) should be improved. Personally I think editing markdown on my iphone is a PITA and for that reason I just put in plain text and edit it later in the Desktop App. This cannot be the way. The only thing where I use markdown on mobile is easy stuff like bullet lists. writing a * is not to much for me But as you already pointed out, typing checkboxes really is a lot of work on a mobile. Also I would appreciated behaviour like “mark some words” - press bold/underline/hyperlink/etc. button - marked text is bold/hyperlink/etc. same as on desktop client - this would be such a usability gain and would also be usable without a toolbar.
Still my question to the developers remains, I am curious: Is the used (buggy?) react native (default?) text input (text area?) component the problem/holding you back from realizing features as discussed here (“do something with marked text”, “implement toolbar”)?