How to Accurately Analyze User Funnel Data on Day 1 Despite Simplified ID Merge Delay?

Hello, I wonder if there is a way to reliably analyze user funnel data between before and after registering using ID Merge. I'm trying to analyze the funnel of first app open -> onbaording -> register complete -> key feature usage -> purchase product The problem is Simplified ID Merge takes up to 24 hours to process, making it difficult to analyze the funnel data accurately for D1. To avoid the 24 hour delay, I tried identifying the new user immidiately with a random ID, and passed that random ID to register it as that user ID. However this method caused a lot of unexpected errors so that would be rolled back ultimately I want to see the D1 (first app open -> onbaording -> register complete -> key feature usage -> purchase product) funnel accurately so we can find where users are dropping off!