I'm using User interface translation in English to override system strings like Drupal 7's String Overrides module did. Works great. However, in my custom module, as I edit strings that run through the t() function, the Source string table in User interface translation is filling up with unused strings.
I'm writing a simple function to delete unwanted source strings one-by-one. The post at http://www.drupal8.ovh/en/tutoriels/89/delete-a-source-string-and-target-translations-drupal-8 provides code for deleting a translation once you know the LID (Locale Id?), which it suggests you get by inspecting the HTML of the displayed User interface translation page.
Question: Is there a way to look up the LID for a source string using the text of the source string?
I've read many posts, but don't see any that suggest how to do this.