Electric Wiper Knob removal

[DavidGB]

Hello virtual PW people. I haven't posted in a while but still have my 47 WDX and 42 WC 53. I decided to look into getting my wipers on the WDX going the other day and immediately realized that it had electric instead of vacuum. I had never looked into the wipers before because I never drive it in the rain. I can not figure out how the knobs come off of the spindle so that the cover plate can be removed for access to the motor(s). There is a small slot in the side of the knob but so far poking around with a small flat head screw driver hasn't magically allowed the knob to come off. The spindle has a flat area that I would assume is so the knob won't spin on it. Yes/no? There isn't any noticeable corrosion and I can get a small amount of wiggle of the knob on the shaft. I don't want to destroy anything. I have to guess that I have to do something with the slot I mentioned but haven't figured out the trick. Any body have experience with these?
Thank you,
David