The VMTN accounts are all backed by MyVMware accounts and I'm not sure if the VMTN activities will merge if you merge the MyVMware accounts.
You can probably change the email ID on the previous account so you can retain the activity.
Either way, please contact VMTN Community Manager @jennivmtn (jenniferg@vmware.com) for guidance on this.
Abhilash B
LinkedIn : https://www.linkedin.com/in/abhilashhb/