I would like to be able to log in to two separate Sandboxes and do a comparison and deploy based on selected changes.  This could potentially replace change sets in the lower environments.

Ex:  I make changes in Welkin and via the UI in my developer sandbox.  I'd like to promote those changes to QA.  By having a comparison I know exactly what's available to either deploy directly, or at least get the diffs to be able to properly set up a change set - autogenerate a change set or unlocked package based on selection would be even better if at all possible.

For an example, please take a look at the SSDT database schema comparison tool in Visual Studio.  It gives the options to deploy diffs directly, generate a script, or generate a DACPAC (package).

https://www.sqlshack.com/how-to-compare-two-sql-databases-from-visual-studio/

https://radacad.com/ssdt-as-a-database-schema-compare-tool

https://www.mssqltips.com/sqlservertip/2804/introduction-to-sql-server-data-tools/