Merging whatsapp database of two different accounts

So, I have two WhatsApp accounts A and B. A has chat history only till December '19 while B's chat history start from January '20. I want to have one account with mobile number that of A, groups of B and chat history combined. For that I plan to 1. Somehow introduce A's chat history to account B by modifying Whatsapp databases. 2. Then doing a change number of B to A. (This step will delete old A account) I want help with the first step. PS: I have looked online on how to merge Whatsapp databases but they all address merging databases of same account here I have to different accounts and also all articles on it are really old.