You can no longer shift+RMB to complete a PolySplit operation in 15.5. Is this a bug or by design? Having to move your hand from the left side of the keyboard to hit Enter is clunky and breaks workflow.

For the moment you could setup a custom shortcut close to the left side of your keyboard. \ seems to be free on US keyboard. But I would submit an RFE cause it does not seem to be a bug.

Having to press enter for almost anything is workflow disruptive.
There was a time when RMB was used for completing things, which was as far as I'm concerned much better, but for some reason (don't remember which) they changed it to Enter.

Regarding PolySplit I just submitted earlier two RFEs: one bug (holding ctrl does nothing) and a feature (see below)

Right now MMB is redundant - it turns off edge snap (they probably meant edge subdivisions since edge snap toggle is supposed to be ctrl) which can be achieved just as well by scrolling down the mouse wheel till it's off.
I propose to have MMB do what you see below: when MMB instead of LMB, you keep your edge origin allowing you to draw other edges from the same point - I use this a lot in Softimage.

@McNistor
that seems like a good feature, I hope it can be implemented! Also I agree with the enter key. Very disruptive.

Okay, RFE for Shift-RMB completion submitted.

And yes, that would be a great RFE McNistor! Beats tracing your PolySplit along edges to get back to the starting point.

Press ‘q’ key to finish off the polysplit and start a new one. Then ‘esc’ key to once you want start doing something else. Works pretty well until the Rfe is implemented.