Hi Melanie,
in general you could enable the smart groups feature within cockpit pretty easily by just replacing AssetsNavigatorModule, with AssetsNavigatorModule.config({ smartGroups: true }), in the app.module.ts when building the cockpit app on your own.
As soon as you activate this, you will also find the smart groups listed underneath Groups in the navigation.
You can navigate to them and will find the Subassets tab where all the matching devices are listed.
All good until here. But in contrast to the devicemanagement application, cockpit offers also further tabs on group level which are not compatible with smart groups (Smart rules, Data explorer and the whole dashboarding functionality).
These three features are relying on the devices/assets having a direct parent/child relationship with the group via the childAssets. This is not the case for smart groups as smart groups basically just store the query that identifies their children.
These features could of course be adapted, but it involves quite a lot of effort to do so.
It could be quite easy to just remove the Smart rules, Data explorer and dashboarding functionality for smart groups in case your only usecase for smart groups is navigating via them or and having the Subassets tab.
Regards,
Tristan