If a user is de-activated, or no longer needs Accounts, Contacts, Leads, or Opportunities assigned to them - you can use the Swantide Reassign Objects feature (https://app.swantide.com/assign) to re-assign the desired Records in a bulk way.
Navigate to the Data module in Swantide and click "reassign objects." From here you will see a list of objects that can be reassigned organized by Owner.
Click on the user that you would like to re-assign their records
Select the specific object that you would like to re-assign, for example, Leads, or you can select All Objects
Then you can simply toggle the checkbox on the individual records that you would like to reassign or choose "Select All"
Currently, you can only select up to 200 at a time. If you are looking to reassign >200 records, you will need to repeat until all records are reassigned.
Select the User you would like to reassign the records to and click "reassign objects"