No, I'm not in the US at the moment. Ok, step by step:
Best to start from an initialisation as the defaults will prevent any other settings you may have done getting in the way of a result
Put your rhythm into composer bank A, if editing a preset use the Pattern Copy function in the composer menu to copy FROM the preset TO composer bank A. If loading a normal Technics style from sd or floppy it usually goes into composer A, if not see later.
Now you can go into this pattern through the composer memory A route on the left hand side of the first page of the composer menu:
choose a pattern; variation, fill, intro etc. press OK.
then press a track; drums, bass, acc 1-5 etc.
and change individual sounds in each track etc by just selecting them from the sound group as the pattern plays. When finished exit out of the composer. Thus each pattern can be edited with new sounds, with different sounds in each track of each pattern if that is what you wish.
Now construct your style in the first 4 panel memories of panel memory bank A:
Panel memory A1 saved with your right hand registrations, balances, tempo etc pointing to composer A variation 1. That is composer A selected in the MEMORY rhythm group and Variation 1 selected under Music Style Arranger. Save the panel memory as normal by holding SET then the panel memory number.
Now save panel memory A2 with different right hand registrations, balances etc pointing to composer A variation 2.
Likewise save panel A3 with composer A variation 3, and panel A4 with composer A variation 4.
Now back to the composer menu and Custom Style Copy. Copy FROM composer A TO a position 1 to 20 in the custom section.
Done.
Exit out of everything, go to the custom section, choose your number and switch Music Style Arranger ON. The 4 variation buttons will contain all your right hand registrations as well as your edited rhythm with new sounds etc, just like a preset.
If you load a normal Technics file from sd or floppy and it ends up in composer B, just repeat using panel memory bank B, then copy that bank from composer to custom. Likewise if composer C. If you load a custom style and want to change it, copy FROM custom TO a composer in the same screen as before, edit the composer, edit the panel memories, then copy that composer back to custom with your new changes.
Good luck.