Lookup Columns give you the ability to pull data from other tables based on a Relation Column that you've created. With a Lookup Column, you can retrieve information from any specified column as long as a Relation Column exists for that table.
Lookups can also be used with multiple relations. For example, say you wanted to show an Image Carousel of all the employees working in an office. First, you would lookup the Photo column in the Employees multi relation. This would bring back all the employees' images and you could bind the resulting column to an Image component.
In the Data Editor, open the table you want to edit.
Add a new column by clicking the plus (+) symbol to the right of the table.
New columns added with the plus button will always appear on the right. If you'd like to add a column somewhere else in your data, you can select the dropdown menu on an existing column and choose Add column right. You can also click and drag columns to rearrange them.
Name the column.
For Type, search for Lookup or navigate to Computed -> Lookup.
Select which Relation column to use as the source.