Hi,
There is no problem to add a new level of categorization. You must add this field in all the forms where the CTI is present and adapt your workflow.
For the forms in CMDB associated with a class, use the class manager to add this field to all the classes you use. If you want to automate this part, you just have to create a script for the cmdbdriver program and then launch this script.
For new classes in the CMDB, when you use the cmdb2asset to generate your form and your workflow associated with your class, you just need to add your field and your workflow in the .txt used by this utility. Then your field and your workflow will be created at the generation time.
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Vincent.