State-field values should be:

0=regular note
1=Next Action
2=Action/Open
3=Waiting For
4=On Hold
5=Done/Completed
6=Someday/Maybe
7=Out-dated/Obsolete

The idea is a more general solution compared to a plain done=true/false value.

Now, it uses alt+F4 to close editor.  However, alt+F4 is usually used to close the  whole program. I suggest fast key for closing editor should be customized or use Ctrl+W

Ability to insert images directly into note's text (not only as attachements).

Ability to assign some tags to be selected by default at program's startup

(regardless of the last tag selection)

I have come across this a couple of times where I will create a list of items and will add or remove items from that list as and when necessary. However it would be easier if the list could be sorted a click of the button. I know a easy solution is to always keep the list sorted by adding the item in the correct place, but there are times when I'm in a hurry and to put it bluntly can't be bothered to work out where an entry should fit.

It's just a thought!