Keeping a submission log
Had to reconstruct a client's submission log recently from emails and attachments going back to 2019. Not ideal. Writing this up partly so I can point future clients at it.
Essential fields: date of submission, receiving authority, product identifier, submission type, outcome. Some firms add a free text column for rationale which is worth doing if you actually fill it in every time.
The main thing is to record contemporaneously. A log that is put together after the fact reflects what you remember, not what happend. And keep superseded entries rather than overwriting them.