Thank you for the clarification of your workflow Michael. Unfortunately, there is not an option to add tabular data from the feature service map into the excel workbook. When a layer is added from ArcGIS Online (in Maps for Office) it serves as a visual aid representation to enhance existing excel data.
A potential solution may be to use ArcGIS Online, add the feature service and use the Extract Data tool to package the layers in your map into datasets that can then be used in ArcGIS Pro, Microsoft Excel, and other products. Extract Data creates an item in Content containing the data in your layers. You can then download the data from the item (see: https://doc.arcgis.com/en/arcgis-online/analyze/extract-data.htm).
I hope this helps!
All the Best,
Shannon