System Settings not responding using Ventura 13.5.1.

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Did you get to try Safe Mode?

I would be flabbergasted if it did not work in Safe Mode.

If it does work, then it would suggest a problem with some third party software.

In that case: Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

By looking at the report we may have an idea of what may be causing the problem.

First, try restarting.

If that does not solve it, try restarting in Safe Mode. Do System Settings work while in Safe Mode?

Restart normally again. Does it now work?

I am glad that you were able to sort this out and thank you for coming back tell us.

Should a similar issue occur in the future, one thing that may sometimes help is to change from Light to Dark mode, or viceversa, as some things may be more visible in one mode versus the other. If I had known that the issue was due to contrast, I would have suggested this trick... in this case, in Dark Mode, the slider is still visible even when moved all the way to the right, whereas in Light Mode, as you have experienced, it becomes invisible.

Snookfin wrote:

Thanks Old toad! I'm probably much older!

Older than what?