On the PC
 
In the Style Browser, to insert filters into the Layer Browser:
 
Double click/Enter on a Style: overwrites all the layers
 
Ctrl + double-click/Enter on a Style: overwrites the selected layer
Shift + double-click/Enter on a Style: inserts above the current layer
Alt + double-click/Enter on a Style: adds the style to the right side of the layer (after) 
 
Ctrl + Shift + double-click/Enter on a Style: inserts below the current layer
Ctrl + Alt + double-click/Enter on a Style: inserts the style at the left side of the layer (before)
 
 
 On the Apple Macintosh┬«
 
There are several different keyboards available for the Apple Macintosh®, but not all of them have the same combination of Cmd, Ctrl, Alt, or Option. However, in PostworkShop, the following keys are interchangeable, even if you have to use the FN key to access them:
Ctrl and Cmd
Alt and Option
 
In the Style Browser, to insert filters into the Layer Browser:
 
Double click /Enter: overwrites all the layers
Shift + double-click/Enter: inserts above the current layer
Cmd + double-click/Enter: overwrites the selected layer
 
Cmd + Shift + double-click/Enter: inserts below the current layer
Option + double-click/Enter: adds the style to the right side of the layer (after)  
Cmd + Option + double-click/Enter: inserts the style at the left side of the layer (before) 
 
Other key combinations that work on PC
 
Ctrl + C: copies the image of the last selected item, layer, object or result image in the viewport. It does not copy the item itself, it copies the image.
Ctrl + V: pastes the image of the last selected item.  You can use copy/paste to work between other programs and PostworkShop and back again.
 
Key combinations that work both on PC and Mac
 
Ctrl + Z: undo
Ctrl + Y: redo
Delete: delete and backspace both work on either the PC or the Mac as expected.
 
You can easily "jump" from the Compositing view to the Style Editor by pressing the Tabulator.