combinepsbt ["psbt",...]
Combine multiple partially signed Bitcoin transactions into one transaction.
Implements the Combiner role.
Arguments
1. txs            (json array, required) The base64 strings of partially signed transactions
     [
       "psbt",    (string) A base64 string of a PSBT
       ...
     ]Result
"str"    (string) The base64-encoded partially signed transaction
Examples
> bitcoin-cli combinepsbt '["mybase64_1", "mybase64_2", "mybase64_3"]'