The Current Layer is the layer onto which any new objects that you create will be placed.
You can define which is the Current Layer by selecting it in the Document Properties Grid, or by choosing it form the Layers dialog.
The objects that go on the Current Layer are the 'primitives' that you create using the drawing tools Line, Ellipse, Rectangle, Text, Cable, Dimension and Insert Picture.
Symbols ignore the Current Layer and symbol references are always inserted on to the Parts layer.
Although it is not recommended, you can move the symbol reference to a new layer by selecting the symbol and changing its Layer property.
The objects that make up the symbol are placed on the layer on which they were created. For example the line and text label that makes up an Audio Input on a block schematic symbol will appear on the Audio Circuit Path layer, while the objects that show the detail of the faceplate in a rack layout symbol appear on the Front High Detail layer.
If the layer on which the symbol reference is placed is hidden, the symbol will be hidden, even if the objects that make up that symbol are on visible layers. In Stardraw Design 7 if a 'parent' is hidden, i.e. a symbol reference or group reference, its 'children' (the objects that make up that symbol or group) are not shown.