I now let the Applet adapt adapt the board to the new piece numbering when you duplicate a piece in the table. I also discovered that it is essential that you define and assign all the morph boards before you press the 'Start position' button. So the procedure is
Duplicate all pieces you plan to use for multiple types, by selecting them and pressing the 'Duplicate' button.
Assign all moves, piece IDs and names that need altering.
Move pieces from the table to the board to set up the initial position.
Identify other pieces that should also participate by selecting those, and pressing 'Add as absentee'.
Define all the morphs, by clicking the 'Morphing & confining' link to call up the morph board, placing the pieces to morph into onto the squares where the morphing should happen, and place holes on squares that should be inaccessible. Assign the designed morph to a piece by clicking the piece its move in the table.
Repeat (5) for all piece types that need morphing.
Press the 'Start position' button.
Press 'Show HTML' to get the Diagram definition to copy to your HTML page.
I now let the Applet adapt adapt the board to the new piece numbering when you duplicate a piece in the table. I also discovered that it is essential that you define and assign all the morph boards before you press the 'Start position' button. So the procedure is