Finding variants modified after being exported

Hello.

While I usually re-export a variant after it has been changed, it's not unlikely that I forget to do that. A property of variants holding the latest change date (I remember that there's something like that in Adobe Lightroom) would be fine, but AFAIK there's not such a thing.

The 'published' flag for variants could be useful, but it is not reset when an already published variant is edited again.

Suggestions?