RSLogix 5000 User Defined Tag Error

I'm working on an RSLogix 5000 v15 applications and when opening one of the User-Defined data types I receive the error:
"This data type was created using Import command and it contains bit overlays. Data types with bit overlays cannot be modified."

I've never seen this warning before. If I wanted to modify this data type would I need to export it, modify it offline and import it again?

Yes - export, modify, import.

Though I hate the restriction. Bit overlays give you the frteedom to treat a tag section two different ways. Very useful.

Do a forum search on bit overlays. They have been discussed and there are some examples.

Usually when I use a bit overlay but I know I'm also going to have other items in the UDT, I first create a UDT that contains only the DINT with the overlay. Then I create a new UDT and include the first UDT with the overlay in it. Since its less likely that I will be modifying the first, I still keep the ability to modify the second.

Good idea, creating just the overlay UDT then including it in a broader UDT.