When a Transaction has been claimed, you can tell as this additional info is shown:
"Gift Aid status - Added to claim on 31/08/2018 Transaction status:Claimed claim submitted on 01/10/2018 Claim status:Claimed"
The one bit of information which doesn't show is the amount of gift aid claimed.
I know you can see this on a Transaction List, but I think it would be helpful to see it in the Timeline, either at the end of the existing message or as an additional (read-only) field in the Allocation section. Maybe next to the Amount Due field.