I've found a way to mass-modify layer name extensions.
Create an attribute file of just the layers you want to change. You must use 'overwrite' rather than 'append'. This maintains the ID numbers so they come back in correctly.
Save the .aat and open it in TextEdit. (On a Mac. On windows, I don't know. Notepad? Strangely, BBedit was actually less cooperative.) Do a find and replace for '.OldExt' replaced with '.NewExt'. Save the file and reopen it in attribute manager. Overwrite the file layers onto the project layers. Ta-daa.
Why? Here's my story. We built a new home for a client way back in AC6. The basement finishing was left for the future, and the future is now.
We differentiate between new, existing, and demolition layers using the extensions N, E, and D. Everything in their project was on .N layers. To begin the basement buildout I want to use our addition template and put the whole existing house on existing (.E) layers.
I can't just merge the old model into a new template, since I would get a bunch of stuff pretending to be new that isn't. I want a clear way to isolate the merged material from the rest of the project, so I can decide as I go what to keep. I decided to give the old project's N layers a distinct extension, 'T'.
Other preparations: I saved a copy of the project, then I trashed the old section markers, since the annotations are lost in the merge anyway, and it makes more layers show as unused. I trashed most of the annotations, dimensions, etc, trying to get a model typical of what we would build for an existing house. I did a 'purge unused' of all the attributes.
Once I've got the old new house merged into the template, I turn on the T layers, hide and lock the N & D layers, hide and unlock the E layers. In the 3D window, I use find and select by layer to move the model elements to their respective E layers. As they are moved they disappear. (Note: one element type at a time. Edit Selection Set doesn't work in 3D. Wish.) It sounds dismally tedious and it is, but it only took about an hour.
Once the T layers are clean they can be purged. If there's any doubt about moving/keeping geometry, the T layers can remain indefinitely since they come in hidden in all layer sets.
HTH,
