On my P2500, that page is available from the Arp button (between Controllers and MIDI).
Also, from Tips and Tricks v. 102 (in the Files section > FAQs, the following might be useful:
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Recording Arp and RIFF Patterns to a Track
Connect a midi cable from the midi out to the midi on of the MP-7, and make sure MIDI Thru is off. You may need to manually erase the 'trigger' note, as well as shift the start times of the arp notes too if they are delayed slightly. Very easy to do with OS 2.0 BTW.
- rEalm
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Recording Triggers
To record into the internal sequencer, set the TRIGGERS destination to be "seq" instead of "int" or "ext" This way, the triggers will be routed to the sequencer, which will then decide where to route it based on the track settings (provided you have Rechannelize on).
- Aaron Eppolito
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If Riffs are set to transmit and you cannot record into a pattern, maybe there's another issue. I will see if I can test it. If I get it to work, that Riff are you specifically interested in (if I have it on one of mu ROMS)?