[Xfce-i18n] Easy way to track new untranslated strings in non-core packages?

[Pjotr]

Is there an easy way to track newly added untranslated strings in
non-core packages?

With the core packages, it's easy: they are all visible on one web
page. Newly added untranslated strings in a core package, show
rightaway.

But this is not the case for non-core packages, like Orage or Postler.
For example: only by coincidence I discovered a few days ago, that
Midori (which I had translated for 100 % into Dutch a few weeks ago),
suddenly was reduced to 98 % because of some newly added untranslated
strings.