Combines the inputs, outputs, and signatures of several PSBTs into one, facilitating collaborative transaction creation and signing among multiple parties.

How is this used?

A group of friends are working together to build a model airplane. Each of them has different parts and tools needed to complete the project. The 'combinepsbt' command is like gathering all these different pieces from everyone and assembling them into one complete model. In the Bitcoin world, a transaction can require inputs (like signatures or approvals) from multiple parties before it's complete. 'combinepsbt' takes these separate pieces—partially signed transactions from different people—and merges them into a single transaction that's ready to be finalized and sent.