Delete button is disable on costumed object.
Right click costumed object, the delete button is disabled. The existing ARQ object can be deleted.
@anon66739973 Only styles that are not being used by any object in the model (and are not the current style, which means that are not the first style that appears when you insert a new object) can be deleted.
Duplicate an exiting object
On Rhinoceros use that duplicate object and delete.
Go back to that duplicate object, see if you can delete that object.
I made a demo, hopefully it’s clear now.
Version: 2.0 WIP newest
@anon66739973, you cannot delete that column style (the duplicated one) because it’s the current column style (the last one chosen when you inserted it).
Insert a new column and choose a different style. Then go back to the column styles dialog and you will be able to delete the “duplicated” column style.