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 


Somehow introduce A's chat history to account B by modifying Whatsapp databases.
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.
Merging two different account in whatsapp is not possible, when you change the number, all your groups will remain same but it can not merge two accounts. Whatsapp backup or restore the chat on the bases of phone number only,when you start new number, it can not recognize it as same account.