There are a couple of reasons to have a removable tongue jack handle. One is to get rid of interference between the jack handle and a truck tailgate. Two, is to allow the use of a drill to operate the jack. I've done this before and I'm not a fan of doing this. If an ordinary, non-impact, drill is used it can just about break your wrist.
An impact drill will save your wrists but I hate the noise, disturbing others, and it's pretty hard on the mechanism.
Access to the internals is very easy. Removing the handle requires punching out the pin. Just because it has a circlip on it doesn't mean that it'll fall out when the clip is removed. It's a friction fit and must be punched out.
Fortunately, for a couple of reasons, the shaft is 1/2" in diameter. A 1/2" x 5" bolt works well as the new shaft. Also fortunately, the head of a 1/2" bolt is a 3/4" hex. So if a drill is used on the stabilizers for fast up and down the same socket can be used for them and the tongue jack. I don't mind using the non-impact drill, which is quiet, for the major moving of the stabilizers and just use the manual crank for the final, under load, adjustments.
You might notice that the hex head isn't right up close to the front of the housing. This is deliberate and allows the socket to fully seat on the hex.
I welded an old Craftsman socket to a piece of 3/16" x 1" flat iron. The length is the same as the original handle. But it could making cranking easier by being a couple of inches longer.
I made my handle on my metal lathe. Pretty crude but it does the job. If I didn't have the lathe I would have probably looked for a short length of fat dowel.
As is for most of my projects, zero cost, made from "junk" that I had on hand.