Logic steals your keyboard input. It does for all plug-ins, not just SD3. However, if you have the plug-in window open and the area you wish to enter text into focused, it should work.
E.g. if I want to start the SD3 Song Track only with Shift+Space, I first click somewhere in the Track tab/area. After that I can click anywhere in the SD3 plug-in GUI and still make use of keyboard shortcuts. Not all are passed on to the plug-in, focused or not. But the rule of thumb is, click where you want the key stroke to be passed in to first.
