eramba is not an inventory tool, please do not use eramba for that ! there are far better tools for that purpose, please read: https://docs.google.com/document/d/1hZ-IVSkad_ohaFcxrM-qN2hDxUrhdHvUX17H4HzRih8/edit#heading=h.3scnhhg7hzni
The only reason assets are documented in eramba is to provide context to risks related to them. how you classify them is a personal decision for that you can use the asset module “classification” options OR custom fields.
If you define a classification you will need to apply whatever that classification is (using classifications or custom fields) too all items on the section, there is no “conditional” … apply this classification options to certain assets and not to other assets.
It seems to me reading this that custom fields will most likely be the best way of action in eramba !