For the majority of direct debits working out when the next one would be due is going to be simple, for example the majority of ISP’s and phone companies bill monthly. So if a payment was due on the 3rd of the Month then you know that it is due on the 3rd of every month. I would assume starling can see the requested date, no matter what date they pay it out, accounting for weekends etc.
All phone companies send bills based on your contract date, they request the direct debit within a certain amount of days from that bill date. Otherwise your monthly fee would be different.
For example my EE is 12th of each month, my Three is 3rd of each month, every statement is dated the same.
Barclays have a sort by Payment date option and a sort by A to Z option although they actually separate direct debits and standing orders in the app and I assume that’s because they can’t easily work out when a direct debit will be paid. I still have a clearer idea of what’s coming up with Barclays than I currently have with Starling, as its simple to click payments by date
Not knowing the exact date isn’t a priority, we don’t know the exact date now. If its due on the 5th of the month, it may come out on the 6th, 7th etc at the moment. It’s only due around that time. So Starling isn’t changing anything if it can’t show an exact date.