I have attached a file "Annex.xml" which is an .xml export from Notepad++.
If you want to give it a try open notepad++ and then go to
Language
Define your language
choose Import
browse to the Annex file
do a Save As to save it
Then you can type or copy/paste code and in the Language drop down choose Annex at the bottom of the list.
It is not Exactly like the Annex IDE but it is very close.
Notepad++ is very handy for writing and editing code.
You can also do a side by side comparison, two windows, etc. etc.
and when you just close notepad++ all your work and open windows are preserved.
You will have to select "Annex" each time you open or start a new document.
The preferences allow you to set a default language but only for the built in languages not for the user defined ones.
dwight