Alter hook for the collapsed summary

+++ b/src/Entity/Paragraph.php
@@ -494,6 +495,7 @@ class Paragraph extends ContentEntityBase implements ParagraphInterface, EntityN
 
+    \Drupal::moduleHandler()->alter('paragraphs_field_summary', $field_definitions, $summary);
     $collapsed_summary_text = implode(', ', $summary);

we should pass in the paragraph, not just the fields.

Also, the man argument should be the first, in this case the sumary.

And the question is how do you actually figure out what is where in that summary?

We should possibly conside to use keys, e.g. field names, so you can actually alter things in a useful way.

Actually, we have an issue already and someone started to work on it: #2868252: Consider adding a hook to Paragraphs::getSummary

Lets continue there. Did not review yet.