To merge all your badges from different account to one account in Salesforce Trailhead, check the below link
https://force.desk.com/customer/portal/articles/2418878-merging-trailhead-accounts?b_id=13478
Note:
Make sure you have the usernames of the accounts which are to be merged.
To link Trailhead & Webassessor accounts, check the below link
https://trailhead.salesforce.com/connect-webassessor?lang=en
Hi I mearged my accounts. Got my badges but lost the link to my adm201 certification. How can I connect all (badges and certifications) in one account.
My https://trailhead.salesforce.com/users/profiles/00550000007a9YRAAY has been deactivated. But the webassessor is linked to this account.
Check this – https://trailhead.salesforce.com/connect-webassessor?lang=en