Just tried it >
https://en.numista.com/vous/votre_compte.php
and at top of that page is
Numista
My account settings
» Upgrade to a premium account
» Reset my password
» Reset my collection
» Close my account
Click on that and the choices are
Numista › My account settings
Collection reset
Are you sure you want to delete your coins and banknotes on Numista? This operation can not be reverted.
· Delete all the coins and banknotes of my collection and my coins and banknotes for swap
· Delete only my coins and banknotes for swap
Guessing that includes Exonumia as well.