I’m not the author or an expert or anything. But I’m fairly sure the joke is about how his license expired and she just made him realize she’s a witness to murder.

I read it as he’s performing a press check in preparation for shooting the person next to him.

Presumably, Bond did a bunch of shooting to get to the point where the comic starts. The gun is potentially dirty enough where failure to feed or extract may be happening. A simple push of the slide back enough to verify that he’s got a live round chambered might save him from having to resort to other methods to silence the other person in the comic.

Not enough detail in the comic to tell whether it’s a striker or hammer-fired pistol.

Most striker (and some hammer) automatics cannot be decocked without pulling the trigger on an empty chamber.

And got those that can, you either have to pull the trigger while holding the hammer back and lowering it manually, or by flipping a separate switch or button.

If it could be done by moving the slide back and pulling the trigger, then holding the trigger down while firing the gun would result in full-auto.

That’s not how you uncock a gun. It is how you would load a bullet into the chamber to take first shot after reloading, or how you would clear the chamber of you want to take the bullet out.

I don’t imagine bond as someone not having the gun chambered at all times though, not sure if there is specific bond lore for that.