Hi, As far as I know, there isn't even a feature for Attachments in the Purchase Order Archives page yet.

In BC21.3, Microsoft once added a part, but did not include Purchase Order Archives.
More details: Business Central 2022 wave 2 (BC21) new features: Access attachments on additional list pages (Attachments FactBox on more pages)
https://yzhums.com/33614/
If you want to customize, in addition to Event, you first have to add Attachments feature to Purchase Order Archives page.
More details: https://yzhums.com/11177/
Hope this helps.
Thanks.
ZHU