When making significant changes to a UDT I find it easier to export a UDT and make the changes in a text editor and import the new or changed UDT. It works pretty well except for 1 minor hitch. Engineering limits are retained for the tags but the enforcement is not.
For example if there is a tag for a tank level with high and low engineering limits entered and “Both” selected for enforcement, upon importing the UDT both the High and Low values will still be there but the enforcement will be set to “None”.