Linking of an external lookup table is adding a link to the external table to the graph. In a graph, you can use internal lookup tables or linked external lookup tables only. So you have to create an external (shared) lookup table first and than you can link it to an existing graph. A single external (shared) lookup table can be linked to multiple graphs.

Right-click either the Lookups group or any of its items and select Lookup tables → Link shared lookup table from the context menu.

After that, a File selection wizard displaying the project content will open. Expand the lookup folder in this wizard and select the desired lookup table file from all the files contained in this wizard.

Linking Multiple External Lookup Tables at Once

You can even link multiple external (shared) lookup table files at once. Right-click either the Lookups group or any of its items and select Lookup tables → Link shared lookup table from the context menu. After that, a File selection wizard displaying the project content will open. Expand the lookup folder in this wizard and select the desired lookup table files from all the files contained in this wizard. You can select adjacent file items when you press Shift and press the Down Cursor or the Up Cursor key. If you want to select non-adjacent items, use Ctrl+Click at each of the desired file items instead.