There should be a straight-forward way to convert a component in the active design to a linked component. Currently this is a multi-step process:1. Save Copy As a new design, 2. Delete the original from the model, 3. Insert the saved design as a linked design and 4. Reposition it to the right place in the model.
There should be a right-click selection "Make linked component" which would carry out the above mentioned steps in a single operation. If there are multiple instances of the component in question in the model, the user should be prompted whether all should be replaced with the linked model.
Further, it should be possible to easily replace an external design with a modified one. I.e. to modify a linked design you could use "break link" to modify the design in its final context and thereafter do a "Make linked component", to replace the previous design (new revision).
Of course, ideally you should be able to directly edit a linked component in the context of the main assembly, see this excellent idea Allow Editing Linked Components but nevertheless a good workflow for making linked components in the first place is beneficial, and the UI improvement proposed here would achieve almost the same as direct editing in the assembly context but with probably considerably less implementation effort.