Hi David
Thanks for posting on the community. Collaborators who have Edit access to the Lucidchart diagram and the dataset used to create it should have access to all layout/data functions including importing refreshing selecting fields setting up filters etc.
You mentioned that "View Dataset" option in the right-hand menu was leading to an empty panel for your collaborator. This is an open bug in Lucidchart causing the panel that this option opens to appear blank for org charts. This is occurring for all users and is not specific to collaborators. Collaborators who have edit/share access to a document will be able to see all of the data linked to the document. In the case of an org chart that data will show in the right-hand panel when a person is selected. For instance below I have Russell Ross selected in my org chart and his data shows in the right-hand panel.
Hope this helps!