Org Installable Apps

Roll-Up Helper

https://appexchange.salesforce.com/appxListingDetail?listingId=a0N30000009i3UpEAI

Mass Action Scheduler 

Create scheduled actions, declaratively and without code.

https://douglascayers-org.github.io/sfdx-mass-action-scheduler/

Declarative Lookup Rollup Summaries (DLRS)

https://github.com/afawcett/declarative-lookup-rollup-summaries 

Enhanced Related List

Configure the Filter, Sort, and Fields on this reusable component on any lookup records to group relevant records in a single page (eg: Open and Closed Cases).

https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3A00000FYDY4UAP