When creating a network analysis layer, e.g. an OD cost matrix, this creates a new data set and adds this to the map. If you click the group layer, this makes the analysis tab open which allows you to import your inputs and run the solution.
My question is, if you remove the group layer or the data source changes, is it possible to add the data set as an analysis layer. If I add the data set to a map, it imports each feature class individually and if manually grouped, it still does not recognise it as network analysis layer and therefore the analysis/solution tab cannot be activated and I have to start from scratch with a new analysis layer.