First post here, so please forgive me if I bugger anything up 
To be able to clearly identify settled versus pending transactions would be very useful to me too. I track expenditure via YNAB and the combination of Mondo and YNAB works well, but I mark a debit card transaction as cleared once it’s been settled.
To avoid cluttering up the transaction feed, as a design suggestion I would subtly change the colour of the transaction value: maybe a grey (similar to the transaction comment) for a pending transaction, while turning black once settled?
There are instances when transactions will never materialise. I’ve just linked my Mondo card to my iTunes account and they’ve authorised £1.58 as part of their active card check processing. The authorisation will expire eventually because iTunes will never settle against it. But currently my YNAB balance is out of kilter with my Mondo card balance.