Why bother with NP++ if you already own sublime, which is arguably equivalent or better, is my question. I use Sublime and I am wondering what feature could be missing to justify still having NP++ installed.

Genuine question, why use both Sublime and NP++?

It does not get more complicated to split your example. What gets more complicated is giving all sort of unrelated responsabilities to a single class, simply because it is the path of least resistance.

In your example, all you need is an extra module listening for configuration changes and reacting to it. This way you leave your context-specific logic out of your data model, no need for cyclic dependency. There are so many downsides to cyclic dependency, to justify it because splitting your logic is “too complicated” really isn’t a strong argument.