So the SP-555 has Effect Memory, right? Well, the SP-606 has a similar feature...

You can control MFX parameters via MIDI CCs: TYPE, CTRL1/2/3 and SWITCH for each of the MFX.

First thing that comes to mind is: arpeggiator.

Could be as simple as controlling Pitch 1 and 2 of the Chromatic Pitch Shifter or as complicated as controlling all of the "Synth Section" (Oscillator + Enveloper) parameters.

Maybe it's old news, but I didn't find any tips or topics - anyone using this?

With the "pad" synth this ought to be very easy, as I assume each pad is assigned a MIDI note, and should work with just using an external arpeggiator to trigger the synth.
With samples, since the 606 isn't able to chromatically tune samples, I don't think this is easy enough to be worth the effort, but I've never tried it.