I was looking at TPL files and I am so used to using a defined language in Notepad++ that I defined my own custom TPL language file. I used the defined keywords, and used some basic coloring for the default layout of Notepad++. If you have a different theme you may want to customize the colors some.
To Import -- download and unzip file, go into Notepad++ and to the Language drop down. Click on Define your language. This will allow you to IMPORT the .xml file. Once you have done that, simply click on Save As... and save it as anything you want to name it. This will then place it in your language listing.
Additions to update v 2.0!
-- Folding Code
-- color coding $$ items that need to be replaced in templates
-- common commands
-- % variables more visible
Working on other editors, just Notepad++ is the one I use the most.