In ArcGIS Online/Portal, when adding content, you can search/view content based on the categories. To do so...
Add > Search for Layers > Click My Content and switch to My Groups > Click the Filter icon > Click one of your Groups > Expand Group Categories > Select one of your groups. Now the content is filtered to only show 16 layers that meet this criteria:
This makes searching for content much easier since we organize the data in our EGDB in a similar fashion.
However, when you're in ArcGIS Pro this option is NOT available. You only have the option to select a Group:
And then it's a 'kitchen sink' approach from there.. No filtering (other than search) or categories available. You have to scroll through all the content:
This is problematic for users that can remember the Category name, but not the actual layer name. As I approach getting my organization to buy into ArcGIS Pro and service-oriented workflows, this may seem small but big for our end-users.