Hi @danmitchell36 ,
You can deposit your Approvers in SharePoint list according to your need, and add a Yes/No type column named Response to record the status of approver response.
If you build your approval process as follows, it might check who has no Response the approval.

Step1: Get items of the Approver List.
Step2: Create action Start and wait for an approval (V2), and append the ApproverEmail.
-If the approver response the approval request, update the item set the Response as Yes.

Step3: Since the number of Approvers are between 4 and 20, and they're approved at the same time. you could set the action of Apply to each by clicking the Settings and set the Concurrency Control as On, and turn up the Degree of Parallelism to 20. So, the 20 approve requests could send at the same time, not one after another.


I hope it can help you. If you still have questions, please contact us.
Best Regards,