I ran into this problem again today and did a search before I posted, which is lucky since I've already asked the question and gotten the response.

XDP6 still seems to work the same way as things did back in 4.0. The workaround of copying the mould shape, removing it and editing as needed, then pasting back still runs into the problem of the result taking on the same mould but not necessarily the same dimensions.

Since the Extrude tool has the ability to temporarily turn the effect on and off it would really be keen to get that action here too.

Off to post in Dear Xara.