How to block an issue transition

If you want the status of an issue to be unchangeable until the approval path is finished, you need to:

edit the workflow in your project to restrict the ability to change status to only a specific user or group,
add an automation rule that will transfer issues status to “done”,
add webhook step to an approval path.

You can give permission to transfer the status of an issue to the admin or you can create a new user only for this purpose.

Workflow settings depend on project type.

Go to Project Settings → workflows
Edit workflow
Add new status. For example, it can be “in approval”
You can allow all statuses to transition to this one or allow only chosen ones
Add transition - from “in approval” to “closed”
Add a condition to transition: click “conditions”
Add a condition to transition: click “add condition”
Select “user is in group”
Select group, in our example it will be “administrators”, click “Add” and publish.
Add an automation rule that will change the status of an issue to “closed”, when an approval path is finished. Remember, the user set as an “actor” has to have permission to change the status of an issue.
Add a webhook step to an approval path definition. In our example, a webhook step will be the last step.

Go to project settings → issue types
Click “edit workflow”
Add “in progress” status
We will name it “in approval”
Add transition to “in approval” status
Select from status “in approval” to status “done”
Add a rule to transition. First click on transition, and next click on add rule.
Select “restrict who can move an issue”
Choose who can change the status of an issue, it can be a user or group. Update workflow.
Add an automation rule that will change the status of an issue to “done”, when an approval path is finished. Remember, the user set as an “actor” has to have permission to change the status of an issue.
Add a webhook step to an approval path definition. In our example, a webhook step will be the last step.