It would be great if the IDE was able to dynamically bring up Salesforce API documentation (Apex, Visualforce, Lightning) based on the code being written or hovered over by the mouse. This would save alot of time by eliminating the need to flip back and forth between the IDE and the Salesforce API documentation. For custom apex classes, the documentation rendering engine could use the associated apexdoc declarations.
Also, would it be possible to have a Salesforce API sidebar to dislplay the references for Apex, Lightning, and Visualforce?