As others have alluded to, certain versions of Logix Designer don't allow editing of safety resources. If you don't have the Pro version, you'll need to either upgrade or buy the safety add-on.
Some might take pot shots at this approach as a revenue-raising exercise, but to me it makes perfect sense. If I had a factory with lots of safety PLC's in it, and lots of maintenance techs and engineers, I'd probably be inclined to deliberately omit the safety add-on from the maintenance technicians computers, and install it only on the engineers computers. Maintenance technicians are always the ones being leaned on to "get it running NOW", and I'd rather that they don't get put in a position where they're being pressured to mess with safety code for the sake of production. Much better for them to turn around and say "it's a safety fault, I can change the guard switch but if you want to edit the safety code you'll have to escalate this to the engineers". Protects the maintenance techs, protects the operators of the dangerous equipment, protects the short-sighted production manager who would have forced an underling into doing something dangerous if they could have.
That aside, the other question is, is the processor safety locked? If it's safety locked, even if you do have the safety editor, you won't be able to change any safety tags or logic without unlocking the processor. Again, this is by design - once safety code is tested and validated, it's locked and a safety signature is generated. That safety signature covers the backside of whoever programmed it. I program safety PLC's regularly, and for each and every one, the safety signature as I left it is recorded. If someone gets hurt on that machine, and the safety signature or its timestamp don't match the one I left in there, I'm not on the hook.