save a snapshot upon exporting?
feature requests go to http://tracker.ardour.org/ If you interested in implementing it, read up on our Lua scripting support (in the manual) and take a look at the examples.
A good candidate to become a built-in feature, meanwhile you can indeed help yourself: There’s an example Lua script which does just that. The script is not bundled with releases, though:
Window > Scripting copy/paste https://github.com/Ardour/ardour/blob/master/scripts/_post_export_save_hook.lua “save”, then install it Edit > Lua Scripts > Manager > Action Hooks
(after loading the script it’s used for the current session, and newly created sessions)