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Keep doing the above steps for the number of layers that you want to assign but remember that the Code will always start with the Forward Slash ' / ' and you need to mention the previous Layers when trying to add a multi-layer option like /Code of First Layer/Code of Second Layer/ Code of Third Layer/Code of Forth Layer and so on.
once Once this window is populated with the required layers, click on the General Tab and then click on the Update button. The window will need to be closed and you will need to click on the Update button again on the Doc Type page as shown in the below screenshot.
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