Here is a screen shot of the second board in the document, showing the end position arrived at after nine tricks:
Returning to the first board, we used Board→Edit to delete North's play to trick 9, and then chose View→Next To Play. In this mode, BridgeComposer grays out the cards already played, shows a blue box around the hand that is next to play and highlights the optimal cards to play in green.
This shows that the best play at this point is for North to discard a heart. If North discards the ♦ 9, as shown in the original document, it causes South to be squeezed on the next trick.
Clicking a card at this point will add it to the Play section, and highlight the next hand to play.
(Optimal plays are determined "as the cards lie" using the double dummy solver included with BridgeComposer.)
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