To properly remove the knob, a stiff paper clip, small flat blade screwdriver or stiff piece of wire is needed. The inside of the knob has a tab with a hole in it for the switch shaft to slide thru. The tab places tension on the shaft and the tension is what holds the knob in place. To remove the knob, insert the tool and try to place it behind the tab - it's sitting at roughly a 45 degree angle against the shaft with the lower half of the tab facing towards the dash. While gently tugging on the knob, pull forward on the tab which will release the tension and allow the knob to slide off. It is not easy and will take plenty of patience!
When reinstalling the knob, be careful not to push it on the shaft too far or it will bottom on the shaft and put a dimple on the center of the knob. Don't ask me how I know...