You might be a king or a little street zsweeper, but sooner or later you will dance with the reaper

src/transaction_builder.h

@@ -77,6 +77,7 @@ public:
     TransactionBuilder(const Consensus::Params& consensusParams, int nHeight, CKeyStore* keyStore = nullptr);
 
     void SetFee(CAmount fee);
+    void SetExpiryHeight(int nHeight);
 
     // Returns false if the anchor does not match the anchor used by
     // previously-added Sapling spends.