No don’t ever run the pixel refresher explicitly unless there are signs of burn-in. Its is never recommended to run as it is reduces the life of the panel however slightly . You can google all about it if you want.
Just let the 4 hourly auto pixel refresher do its job.
You will not find it anywhere. But I know how to see that the pixel refresher is running in standby.This is how-
Always keep a usb powered external hard drive with led connected to the usb 3.0 port. When you put the tv on standby; If the hard drive led stays on then it means the pixel refresh is running and it takes around 6m30s (approx) to complete the pixel refresh after which the led on hard drive goes off.
When the pixel refresher is not running the led light on the hard drive will go off almost immediately on putting the tv on standby.
I generally turn off the tv after 10 mins in standby.
You can test it , this cycle repeats every cumulative 4 hours.
Works on C8, no idea about other variants.
I also had this issue, now I am at just over 100 hours and its now gone completely.