Portfolio Start Date

Is there currently a way to establish a Portfolio Commencement Date? When comparing performance to a benchmark, it can be good to establish a preferred date, especially if there has been more than one tranche of funds in establishing the account, for example rolling more than one super fund into a newly established account.
As an example:
New Fund was started on 17 August 2023 with a balance of $10,000. There was another transfer in on the 19th August 2023 of $20,000, and a final transfer in on 25th August 2023. Investments were purchased on 31st August. For reporting purposes a start date of 01 September 2023 may be selected.
Currently there doesn’t seem to be a way to note/select a start date for reporting purposes, apart from the date of first purchase.
Very happy if I am wrong and there is a way.
Many thanks,