Simple N-Panel
Does it slow Blender down?
No. It reads which panels are registered and keeps a short list in your preferences — that's all it does. No scene data, nothing running in the background.
Does it need an internet connection?
No. Simple N-Panel has no network access and no external dependencies. Nothing leaves your machine, which also makes it easy to clear with a studio IT policy.
Can I install it on more than one computer?
Yes. It's a one-time $10 purchase under GPL-3.0-or-later, and you can export your tab layout to a JSON file and import it on the next machine —order, names, and visibility come with you.