Merging records has been updated and improved in Unified Interface
|Enabled for||Public preview||Early access||General availability|
|Users, automatically||-||Jan 24, 2021||Apr 5, 2021|
This new experience was introduced in October 2020, but it required admins to enable it. Coming in the April 2021 release, this feature will be the default user experience.
Duplicate records can happen in your data when users create or edit records manually or import data in bulk. Now, when a duplicate record is detected, you can easily merge data and retain the record you want. You can also choose up to two records to merge from the view or list page and merge the data into a single record with the new Unified Interface merge record dialog experience. When you merge a record, any related or child records are also merged.
Merge records from a grid (docs)