Hi JHvw,
I go through the post carefully, in Excel for Mac there could be not built in Data entry forms in Excel for Mac, I would suggest you vote and leave your comments under the feedback thread in Excel Feedback community: Restore data form functionality (different from VBA UserForms) · Community (microsoft.com), the related team of Excel are aware of the requirements, though the feature is not in the plan now, your feedback will address the feature and will promote them to develop it. Thanks for your patience and understanding!
As a workaround, you may create data entry form with VBA, you may find related discussions on this from the link: Data Entry Form in Excel- Office 365 for Mac - Microsoft Community
Best Regards,
Clark