We just have one general 'patchwork' layer where we put our 2d patchwork. There doesn't seem to be much need for it.
2d furnishings go on the same layer as the 3d work generally.
In rare cases I've used 3 different layers for stairs. One for stairs that have a good 2d symbol and good 3d model, one for 3 models only and one for 2d line work only, but I can only think of two projects over the course of 9+ years.
For annotation we use quite a few scale and 'topic' layers.
Erwin Edel, Project Lead, Leloup Architecten
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