Is the toggle there?
Should it be added if not?

Not.
(Once you start editing, it auto-becomes enabled. Then I guess one will use the gesture to continue tweaking it quickly. No real need for a quick way to toggle if off/on I think, and out of my simple scope :))

No real need for a quick way to toggle if off/on

IMO, one might consider tweaking it, and then using the toggle to quickly compare with and without tweaks to see how much it changed.

and then using the toggle to quickly compare with and without tweaks to see how much it changed.

OK, you have it, and "Toggle all enabled style tweaks" if you really want to see how much changed.

"Toggle all enabled style tweaks" --> "Toggle all style tweaks"?

Also, previous notifications have followed the format Feature: on | Feature: off. This one does On|Off: Feature.

We should probably agree on one common style?

"Toggle all enabled style tweaks" --> "Toggle all style tweaks"?

"all" feel ambiguous: will really ALL styletweaks become enabled ?
"all enabled" make it clear we will toggle only those that are/were enabled

Also, previous notifications have followed the format Feature: on | Feature: off. This one does On|Off: Feature.
We should probably agree on one common style?

I guess for style tweaks, if was On/Off: name of that style tweak because these names can be quite long, and we want to be sure On/Off is shown. @hius07 ?
For these "book/all tweaks" actions, I decided to have them look the same as for individual tweaks, for consistency (among style tweaks, rather than globally).

"all" feel ambiguous: will really ALL styletweaks become enabled ?

Or just "Toggle style tweaks"?

these names can be quite long, and we want to be sure On/Off is shown

I agree with this reason.

Or just "Toggle style tweaks"?

I'm fine with this one.

"Toggle currently used style tweaks"?

However, this will be ambiguous after the first toggle.

Situation:

1. User has N style tweaks in use.
2. User activates "Toggle currently used style tweaks". They all turn off.
3. Now there is no indication of what tweaks are "currently in use". Does the Dispatcher remember which ones to activate if the user activates the toggle again?
4. Should there be an indication in the top menu style tweaks list of what tweaks were disabled? Or otherwise how to notify the user that all of those tweaks were disabled by the toggle?
5. What is going to happen is the user toggles OFF all the tweaks, then turns on a select tweaks from the top menu, and finally hits the toggle again? A) old tweaks disabled by the toggle get reenabled; or B) the history of old toggles is removed and now those newly turned on tweaks get disabled.

Sorry for making it probably harder than it is, I am just trying to think about "foot gun situations" when using this toggle.

IMHO, only having a toggle for Book-specific tweaks would suffice - this is a quick trial and error playground, whereas style tweaks are more permanent solution (usually found in the end of Book-style tweak back and forths).

It's the same toggle that already exists in the top menu: Enable style tweaks (long-press for help)