Step Sequencer and
Matrix View were so broken in Sonar that I gave up on them long ago, but maybe things improved recently?
The lack of
Track Templates in Studio One is mildly annoying; I work around it with a combination of larger song templates and FX Chains. In practice it's not been as much hassle as I'd feared.
Lack of
gain knob was mildly irritating but it's trivial to increase the gain on a clip (drag the handle at the top) and if that isn't enough, I add an EQ as an insert and just adjust the overall output gain.
Event Editor... never used it in Sonar except to look in vain for rogue events that might have kept it playing past the end of the song... so not sure what an S1 equivalent would be.
Mix Recall - no equivalent as far as I know, sorry.
Groove clip - if you need to copy a loop, hit D to duplicate it. If you need to stretch it, hold Ctrl and drag the end (or Alt - I forget). Studio One also supports some sort of loop format and I expect you can convert a clip to that format if you really need the drag-to-repeat functionality? (Not sure though.)
Clip property information in Sonar Inspector window - does the Studio One Inspector not show what you need?
Special copy paste - I used this in Sonar because non-special copy/paste was worthless. What in particular do you need from this?
Link Clips - hold Shift and press D to duplicate a clip in 'shared' mode.
Waveform preview for instrument tracks - yeah, not sure there is an S1 equivalent. Maybe after 'convert to audio track' but that's basically bouncing it.
Alt+click a bus track to select all tracks routed to that bus - not sure about this. There's a little indicator somewhere in the console view showing how many tracks are routed in there, so maybe clicking randomly on that with shift/alt/ctrl might do something ;)