As discussed in: http://talkgraphics.com/showthread.php?p=368292

It would be very handy to be able to select inside of a mould and edit the contents as normal without removing the mould first, as some steps may be required to get things back to where they started.

Since that would be challenging, a good compromise (to me) would be a button in the Mould Tool similar to the one in the Extrude tool that could temporarily remove the envelopes applied for editing, and then reapply them to get back to where you started from.