I was translating www_www.po and wasn't finding the strings that were missing for the 5.18 announcement to get 100% translated.

Ilya Bizyaev mentioned posieve can filter strings in such a way that allows to find all strings related to the 5.18 announcement, the same string that appears in the Unit Metadata pane for Files in Lokalize.

With the following command provided by Ilya, the Brazilian l10n team managed to find the missing strings:

posieve find-messages -scomment:'plasma-5.18.0.php' www_www.po -slokalize

Which, when run after having Lokalize open, searches for the correct string and sends the results to Lokalize so the translator can find all missing strings.

This is a really useful functionality that would help fully translate KDE announcements in time. Currently the only way to verify whether something is missing is to wait a full day until scripty runs at around midnight, which is really inconvenient as there are at most only 5 days before the announcement for translators to do their job prior. Spreading the word on pology to all localization teams is possible, but it would be more efficient to simply implement this functionality in Lokalize.