This use case prevents issues from being closed if there exist blocking issues (linked with "is blocked by") still not closed.
Add the Validation of linked issues to the desired workflow transition.
Select is blocked by (Blocks).
Select Closed.
Select one of the possible options that work best for your case.
Check the following options:
Checking this option allows you to skip the link types filter.
Checking this option allows you to skip the issue type filter.
Checking this option allows you to skip issues with resolutions.
Validation of linked issues