Microsoft Advertising has updated its help page to include campaign-level tracking for Performance Max shopping product URLs.
The help page outlines that dynamic parameters such as {AdGroup} can be used in campaign-level tracking templates to populate asset group values.
A sample UTM string is provided, demonstrating how tracking can be structured to optimize performance for shopping campaigns.

See the help page for more details: Microsoft Advertising Documents Campaign-Level Tracking for Performance Max Product URLs.
This update was uncovered by Hana Kobzová.