I did not use any IDE. I just edit the files directly.
The basic question is: is your widget based on svg drawing? or it is based on non-svg components?
For non-svg, I suggest to find the closest existing widget from the widget gallery, and modify it.
For svg drawing, I relied on the knob provided in habpanel, but also on the excellent [Custom widget: Gauge].
I make sure the main js file (ng-knob-thermo,js) is independent of OpenHab, so it can be tested by itself (index.html). Then, all OpenHab related stuff is placed into a control file (control-oh.js).
If you have a svg based widget you want to do, maybe this widget can be used as a template. I’ll be happy to make suggestions if you have a specific design you want to do from there…