I use Sublime for Hise code search and mods, and to open, scroll and pick up code from sandbox projects.

However I don't use external editor for the project itself and do everything inside Hise.
The reason is that in the past when having files opened in both Hise and external editor, if you accidentally recompile Hise it overwrites your changes in the external editor (since the files are saving on recompile)

This was before the new Hise script editor anyway so no need anymore
Hise editor is now super powerful (minus just a few minor bugs). Having the double click on the API list to insert back would be awesome.