How can I stop a device appearing in Wireless?

If I click on wireless on my main menu and then 'group by' controllers I get every device that is capable of being a WLC.

However, I'd like to restrict that to just the devices that are actually acting as WLCs. As an example, most Fortigate FWs are capable of being WLCs but in pretty much every usage case (for us) they aren't. So I'd like these not to appear and wondered if there was a method to achieve this?

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