|Manage → Layers|
|This command is part of the BIM AddOn, that you can install via menu Tools → Addons Manager|
The layers manager allows you to manage layers. Layers are a special kind of group that controls the visual properties of objects placed inside of it. By changing the properties of the Layer, such as line width, line color, shape color and transparency, the changes are propagated to its child objects. Layers don't interfere with any other FreeCAD structure such as groups or Building parts, so any object can be at the same time part of a layer and part of a group.
The layers manager allow you to manage your layers, add or remove layers, or change their visual properties. To add objects to a layer, simply drag them into the layer in the tree view. To remove them, drag them from the layer and drop them into the document root.