Hi Dennis, and welcome to the forum!
I am sorry you are having trouble with the pictures. I have problems posting pictures here too, so I usually just post a link to the picture stored somewhere, like in a Dropbox account. I believe in the introductory sections there is mention of another type of online photo storage you can also use.
Electromechanical sounds intriguing, and fancier than the design I am currently making. So I'd love to learn more about it. If this type I am making works out I'll post it on here with some photo reference. Basically it is rather simple. I intend to cut the unthreaded part of the leadscrew (hidden behind the control box) and remove enough to leave a 1/8" gap in the shaft after facing the cut ends. I'll then make a custom washer to fit this gap and set its thickness to assure there is no leadscrew endplay.
In between the cut ends, and through that washer, will be inserted a piece of 5/16 drill rod, to keep the two halves aligned. Two 1/8" dia. by 1" long spring steel roll pins will be inserted crossways through the leadscrew shaft, so their ends stick out. One will pass through the short piece of the leadscrew AND through the 5/16 "pilot shaft" between the leadscrew cut ends. The other will pass through the leadscrew shaft just off the opposite end of the 5/16 shaft, so the long piece of leadscrew will be free spinning on the pilot shaft as long as the clutch is not engaged.
As a clutch, I am making a sleeve that will slide over the leadscrew. The LH end of it will be slotted through both sides, with the slots running parallel to the shaft, and long enough to allow the sleeve to slide past the exposed ends of both roll pins in the engaged position, sliding the sleeve toward the gears. To disengage, the sleeve will be slid back toward the chuck, so that the first roll pin is no longer in the slot. The RH end of the sleeve will stick out just enough beyond the RH end of the control box to grasp a raised ring I'll turn on the end of it, as a sort of knob. I'll have to enlarge the control box cutout for the leadscrew.
I don't anticipate the sleeve moving on its own. But if it does, I have some ideas how to prevent that.