Please add autocomplete as well as dropdowns for attribute values. My workflow often involves choosing particular value names as values. In this case, if I type the value with a different capitalisation or when I make a typing error it is often difficult to diagnose at first glance what went wrong.
With an autocomplete per attribute key, I could reference an existing attribute value for a given key. With a dropdown, I could pick and choose an existing value. Both would really help with complex naming schemes as well.
In addition, it would help with Revit interoperability in Rhino.Inisde.Revit, where you have a similar system with dropdowns to set attributes values such as the wall height, alignment, wall type, etc.