How to I get an External List in Datasheet View? I have a List, whereby I have Looked up a Column from an External List. The column appears as readonly in Datasheet View, but behaves normally using the normal view.
This is one of the limitations of an external list; there is no way to get a datasheet view with the built in functionality of SharePoint.
Other limitations are quite well ennumerated on this blog post. As you can see, there are quite a few of them and it is worth bearing these in mind when designing solutions with the Business Connectivity Services.