This is done with the F2 lookup feature. Almost any field can have an F2 lookup value.
More info can be found here:
Thank you for the quick response.
You are correct!.
I'm looking to have a Custom Field, however as a drop-down list. I have checked the forums and couldnt see anything about this being asked.
Essentially, are there any plans to add in custom fields which allow for a dropdown of options.
Like the Profile field, which allows a user to define a list of options.