Man pages matching name tshttptxnclientpacketmarkset in section 3ts:

TSHttpTxnClientPacketMarkSet.3ts.en	debian 10 / trafficserver-dev
TSHttpTxnClientPacketMarkSet.3ts.en	debian 11 / trafficserver-dev
TSHttpTxnClientPacketMarkSet.3ts.en	debian 12 / trafficserver-dev