@dostovel You link a collection the same way you would a ‘Group’
‘Groups’ are planning a comeback, but they will be different to the old groups.
Collections, have a few issues when they are linked. eg – you can’t drive the visibility once it is an instanced collection, and when you make a proxy, the name of the proxy is the name of the Collection, not the name of the object in that collection that you proxified…..is that even a word? Is now!
Also there is no way to hide objects in an instanced group (linked or local) like you could in 2.79.
I’m hoping all these quirks will be fixed.
