Validation rules allow you to enforce data quality by preventing users from saving records that do not meet certain criteria.

Two ways that marketing users can now access converted leads for editing are:
Find them in the global search result, by entering the lead name or other keywords in the global search box and selecting Leads from the drop-down menu. Converted leads will appear in the search result with a check mark icon next to them.
Utilize a list view where lead status equals Qualified, by creating or modifying a list view on the Leads tab and adding a filter for Lead Status equals Qualified. Converted leads will have Qualified as their lead status and will be visible in the list view. Searching the Recent Records component on the homepage or using Data Import Wizard will not allow users to access converted leads for editing. Reference: https://help.salesforce.com/s/articleView?id=sf.leads_view_converted.htm&type=5

Case escalation rules are a way to automatically escalate cases that meet certain criteria, such as being open for more than a specified time or having a certain priority. Escalation rules can assign cases to a different owner or queue and send email notifications to the support manager or other recipients. Reference: https://help.salesforce.com/s/articleView?id=sf.case_escalation.htm&type=5

Log in as the user is a feature that can be used to validate the error the user is receiving. Log in as the user allows an administrator to access Salesforce as another user and perform actions on their behalf, such as editing an opportunity. This can help troubleshoot issues that are specific to a user's profile, role, or permissions. Reference: https://help.salesforce.com/s/articleView?id=sf.admin_login.htm&type=5

The mass transfer tool allows you to transfer up to 250 records at a time from one user to another user while keeping the existing team members intact. You can access this tool from Setup by entering Mass Transfer Records in the Quick Find box. Reference: https://help.salesforce.com/s/articleView?id=sf.mass_transfer_overview.htm&type=5