When you create a new attribute , one of the control types is Selector. This lets you create a new attribute that points toward pre-existing tables. This works well in many forms, but the functionality is not present if the attribute is put into the system as a project attribute or task attribute. Would like to see this functionality added to the system.
Example: I want to create a 2nd project manager field on the projects form. I call this field Senior Project Manager. I create this as an attribute and designate the control type as selector, then choose CREmployee as the schema object. When I use this new attribute as a project attribute, it becomes a simple text field and does not let me chose from the Employee list. But if I were to use this attribute as user-defined field in the bills and adjustments form, it does function properly and let me select an employee from the list.