Hi,
There is one way of doing it which might help you.Have a duplicate window(CTRL/CMD_ALT/OPT+K or Windows>Duplicate window) open undock it and place it beside the original so that both windows are seen.Double click the symbol in duplicate window and work on it.You can see the resultant effect on the main timeline in the original window.But scrubbing timeline in duplicate window does not move the play head in original window simultaneously.You need to do this manually in both windows individually to see the resultant effect.Hope this helps.
Thanks,
Sangeeta