I believe you would have to add a screen in the approval transition with the added fields. If you add approval screen at the transition you should be able to add the fields you want to require.
1st Go and create the approval screen and add fields you require during the approval.
2nd Then go into the workflow and click on the approval transition. At the bottom of that transition edit you can add the approval screen you just created.
After they approve the issue by hitting the green approval button it will kick the screen approval screen during transition.
hope this helps.
From what I seen your question was originally it seem that I had answered it with adding the screen and fields to this new approval screen.
Now looking at the jira request gathering it seems you needed this to be a required state which is not yet available for an option.
In the screen configuration you can add this to the portal as a transition but has stated it can not be required.
I hope this finds you well and soon is implemented by Atlassian as I myself have needed that option.
Hello Atlassian Community! We’re thrilled to announce some exciting changes to incident management in Jira Service Management Cloud, in order to give your teams extra muscle during incidents, and ...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events