Have you searched existing Github issues to see if someone has already requested this feature?
Yes

Is your feature request related to a problem? Please describe.
I like that Heynote is very "keyboard centric", so you can quickly add/paste and move around blocks and buffers using just the keyboard.

But when you have some Markdown checkboxes, the only way to toogle them (that I found) is by using the mouse.

Describe the solution you'd like
I would think a hotkey that toogles the state completed/non completed in the positioned line (only when is a Markdown block and the line had a existint checkbox placed) would helps to avoid to switch to the mouse just for clicking.

In other software (more Tasks oriented) the same hotkey could convert a normal line in a task one (that means, if the line does not have a - [ ] it insert it and then just cycle the toogling between checked/unchecked but maybe that could be out of the scope of this software and could be handle it by text expander software.

Describe alternatives you've considered
Using atohotkey to make that switch (altough I don't know how)

Thanks!