For this spider leg, I want to achieve procedural movement in Spine using the latest Transform Constraint features.
Even achieving a single step-jump toward the movement direction would be a success for me, since my goal isn’t to create something realistic, but rather to practice and explore the limits of the new Transform Constraint
Can you post the project file and images?
You beat me to it! 
Also changing Y is a nice touch.
Getting multiple steps seems hard, or impossible.
Nate as @warmanw says It would have to be duplicate the two constraints then change the input/output values or I think you can just offset the Translate X each time. That offset would be the exact same every time also. ie, duplicate these two constraints and add or minus 40 (the total range of the constraint inputs) to the X offset, repeat).
It feels like there would be a programmatic solution there since it's a repeated step, but it's also probably a very limited use case for the editor itself.
It's basically a 'cycle' mode for linear constraint inputs (like translate) that allow for a constantly increasing input to 'clip' itself back within a relative range, kinda like how an angle would go from 0-360 but 360 sets it to zero again rather than continuously adding to the value every rotation.
Harald had an idea for transform constraint to have a modulo setting. That might be interesting for repeating a range.
Erika has an interesting sort of solution, but I'll let her show it so I don't steal her thunder. 
I think I found a viable solution that takes advantage of rotation to achieve the foot movement:
This was a fun challenge!
Super cool, thanks Erika!
Harald had another idea: 0-360 world rotation already does modulo. He made a similar version with a pause between each step:
You're a wizard, Harri! 
He bequeaths unto you these clues:
in theory the trick is splitting the 0-360 degree range into 0-180 for subtracting e.g. 50 from the controller first, and a second time 180-360 for adding the subtracted 50 back in in the second half. thus there are no jumps at the loop transition
in theory this can be done not only with halves, but also splitting [0-E], and using [E-360] to catch up
It's really neat to see the clever things that can be done with the new transform constraint! At the same time, this gets pretty complicated and it's not easily approachable. It's almost like building a clockwork robot! We have more plans for 4.3 that should be very powerful in a more straightforward way, though I'm not sure it could do the "automatic spider step with a pause".
Thanks for the credits Nate! I just extended Erika's version, so half the work was her's 
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Also played with the same thing but in a slightly different way.
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