I think it would be really handy to be able to select a transaction and have the option to move it onto your joint account from your personal account. There have been a few times where I have automatically grabbed my personal card to buy things I would usually have put on the joint account.
Sounds like you need a Curve card.
The ability to move transactions from your personal account to a business account (and vice versa) is on @jackcully and the business banking team’s roadmap as “Move expenses paid on personal account to business account (and vice versa)”.
Hopefully, when this feature is built, the ability to move transactions from a personal account to a joint account (and vice versa) will be included.