Idea for new Export PSBT button to match functionality of Import PSBT button

[tomunchained]

It would be nice to have an "Export Current PSBT" button on the signing page, that includes any signatures that have already been gathered in the downloaded file (and one wouldn't need to unnecessarily enter the Coldcard flow).

That way, the file could be shared with a collaborative multisig parter, who uses the "Import PSBT" button to stage the transaction with all current progress, apply additional signatures, and then broadcast or continue to pass it along.

[jevidon]

This option should appear on both the "Preview Transaction" page as well as the "Sign Transaction" page. Suggested locations marked in red on the following screenshots.

Stretch goal: update the CTA's on the "Sign Transaction" page to be the color button style as seen on the "Preview Transaction" page instead of just a text-based link.

[Shadouts]

I think it needs to retain the option to not include already gathered signatures. Including gathered signatures reveals information about who has signed and may not be desirable if the operator merely intends to gather signatures from other parties to combine and broadcast on their own. This can be easily achieved with an option menu (menu button).