Disabling the driver doesn’t make anything un-editable. (And if it did, edit then disable-- if its disabled, you’re not tuning to eye anyways.)
Open a driver editor viewport. Select your object. Select your driver, on the left hand margin of the driver editor. Next to your driver, there’s a checkbox, with a tool tip labelled something like “contribute to f-curve.” Uncheck that box. If desired, continue on to edit your driver (probably, using the sidebar on the driver editor viewport.)
In this case, I’d like to toggle between the driven state and the undriven state to take a quick look at the undriven value at different points in the timeline, so as to better adjust the expression within the driver.
Basically, I want to skip any typing from toggling back and forth, since there’s a PITA expression inside the driver.
So, does this “contribute to f-curve” box essentially function as a enable/disable toggle?
This link shows a ‘speaker’ icon that apparently “mutes/unmutes” a driver, but it’s a further down the rabbit hole than I know how to follow.
I post it just as a point of interest. (Also, it’s from 2017 so it may not apply any longer.)
OK, the checkbox seems to have replaced the little speaker (which IMO was cuter). There IS a behavior that I find surprising, but neutral, and that other users may find convenient and/or useful:
it seems that when you disable the driver, whatever the last evaluated value for that particular frame is retained in the parameter as a constant. IOW, the driver stops working but the last evaluated value stays. SO, users must be aware of what frame they are on before clicking that box willy-nilly. AND, do NOT expect to see a visible change in something’s behavior when toggling the checkbox (that was what was throwing me).
If that’s the case I can see how it might be (very?) useful in settling on a particular value before deleting a driver.
I’m still a little blurry on the difference between the little wrench and the checkbox but I’m sure (ha!) it’ll all be clear eventually.
If you have keyframes for the object, the object will be reset to keyframed values. If you don’t, disabling the driver doesn’t do anything to restore a position (or whatever)-- there is no position to restore without keyframes, only where it is.