I agree that threads should have a common family theme, so it has been practice within the group for children's birth to be posted on the thread for their parent's marriage. Big compilation threads become trickier.
I have found efficient ways to search compilations and other long threads:
1. In the top right of each thread is a button with two arrows pointing up and down - if you hover over this it gives "Expand All" as the instruction. Click this.
2. Every post is now visible in the thread. Press CTRL + F keys together (this accesses the search function in most browsers on a computer; if you are using a phone or a browser where this doesn't work, you will need to work out how to do this). In the search box, type the name / text you are interested in and it will find all occurrences in the thread which you can cycle through.