The Symbol Layers sub-menu lets you define which is the principle layer into which symbols are inserted. By default all symbols are referenced by a layer called "Parts". Although no drawing objects like lines or text are ever visible on the Parts layer this layer is vital to the operation of Stardraw A/V Lite. Because it references every symbol it must always be visible and each of the preset views ensure that it is visible. If the Parts layer is not displayed, any symbol which is referenced by it will be invisible in all other layers.
If, in the Symbols Layer menu, you select "Work Layer", new symbols will be referenced by whichever layer is your current active or working layer. This can be useful if you have a requirement for layer-selective reporting or wish to tie products more closely to layers. For example, if your current layer is "Video Circuit Paths" and you set your symbol layer to be "Work Layer", all symbols that you add from this point forward will exist on the "Video Circuit Paths" layer. Then, if you hide that layer, the symbols will also be hidden.