Ability to sort by content size in the Manage page
Add a filter or sort for SharePoint size
My deletion logic is filter by no owners and no members. If site size was there I'd also sort smallest to largest. I'd then delete the majority of them and discuss larger sites with colleagues before deletion.

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Bill Buhl commented
It would be helpful to sort and categorize Teams and Groups in the various views on the Dashboard by their size . We can also use this to target inactive groups for clean-up or for labeling.
For example if a group has a long term archival storage purpose, but is relatively inactive, we label it and know it's not old and unwanted data. But another group for an old project that isn't used could be cleaned up.