Once I create a UDF with a drop down list and associate the list to the UDF, I can't edit the UDF to change lists if needed. I should be able to associate a new list to a drop down UDF.
A related capability would be a rule that would change the list based on a condition:
If the project is "x" then use list PhaseX, for project "y" use list PhaseY. Hopefully that makes sense but that's what we do in ALM QC today. Switching lists based on status or group or other values makes the process more flexible
The rule to change lists IS availble for a limited number of fields but doesn't include UDFs. For defects it's only available for a handful of fields.