We already have an inputChangeHandler set for this, caught in the else.

What you could do is move the above if ( key === "linkUrl" ) block, and put it into a new if block just before the else, that sets up a input handler. See how we do the shadowColor and backgroundColor disablers.

So you move it down into one block, and add your own callback, which works a lot like the checkboxCallback, which calls the update after it does it's thing, so you no longer have to go into the catch all input handler.

You'll probably want to add something like linkUrl to pickers, just like background and shadow.

Anyway, follow the background and shadow pattern, ping me if you have questions as it is a lot to soak in, and try to keep all changes in this file.