The joinpsbts RPC merges multiple distinct PSBTs into a single PSBT. The multiple PSBTs must have different inputs. The resulting PSBT will contain every input and output from all of the PSBTs. Any signatures provided in any of the PSBTs will be dropped.
*bitcoin-cli help joinpsbts
joinpsbts ["psbt",...] Joins multiple distinct PSBTs with different inputs and outputs into one PSBT with inputs and outputs from all of the PSBTs No input in any of the PSBTs can be in more than one of the PSBTs. Arguments: 1. txs (json array, required) A json array of base64 strings of partially signed transactions [ "psbt", (string, required) A base64 string of a PSBT ... ] Result: "psbt" (string) The base64-encoded partially signed transaction Examples: > bitcoin-cli joinpsbts "psbt"