On Land

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At Rill Architects we run ArchiCAD on Mac OS X. If you work at Rill, this is your stuff. If you don't, but you work in ArchiCAD, you may find something interesting. Anybody else, I don't know.
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The Active Layer palette is accessed on a submenu of the Layers submenu, which might be on Options (9) or Document (10) or somewhere else by now. You mean the Quick Layers palette? No. Active Layer.

This palette does exactly one thing, and I use it for exactly one purpose. It switches between the default state of 'Individually Set Layers' and the weird state of 'One Active Layer for al Element Types'. That is, it can set all the tools to the same layer in one go. And it can put them all back to the layers they had.

No, I wouldn't want all the tools on one layer, ever. I don't know why they made this thing, but here's what it's good for. Attribute Manager will report that a layer is in use if it is the current default of a tool. So you can't really tell if an element is on the layer or not.

So, use Active Layer to set all the tools to the Archicad layer. Set the palette to 'One Layer' and then set any tool to the Archicad layer.

(The other source of phony checkmarks in Attribute Manager is Favorites.)

When you close the Active Layer palette, or close a project where all the tools are 'One Layer', you'll get a dialog asking if you want to keep the One Layer, or Revert to the individual layers. You should choose Revert. (Of course, if you've deleted most of the layers, there's nothing to revert to, but it doesn't matter.)