There are several reasons for having a View/Edit button in our (rather limited) editor:
a) Our editor has a limited line capacity, so extremely long files get truncated – so you need to use an external editor to even view the end of those files (error logs for example, or even the Final SFM file)
b) AFAIK you can’t zoom in on the text, and some non-roman fonts/scripts appear too small to read easily, so people often open the file in their preferred editor
c) Other editors allow a whole host of editing power (keyboard shortcuts, find-n-replace, and even RegEx capability) which we don’t plan to offer in our rather basic viewer.
However, if you are using an external editor to edit settings, you do need to be careful to save (in the external program) and then refresh the file (withing PTXprint) before you save. Otherwise you are likely to lose your changes.