Success!

I can now record sequences from Encore into the Synclavier with Synclavier^3 in one pass. I discovered all of the manuals at Synclavier.com and have been going through them to find the changes between Release M - which I was using thirty years ago - to the new Release 5.3. Many things have changed, of course, and it turns out that, in order to prepare multiple tracks for recording, you press and hold the MIDI button, and then press the tracks you want to record.

I still have not gotten synchronization between Encore and the Synclavier to work, but that is not strictly necessary, so I'm going to give up on that for the time being. Once the sequences are in the Synclavier, everything will be synchronized to itself anyway.