Hi,
You want to have your certifications linked to personal Microsoft account (aka MSA). I've seen where people had their certification linked to work account and lost it after leaving their employer. Don't know if MS has fixed that.
I'm unsure of answer to your specific question. Mainly, if you register for exam with work account and email address and then later link personal MSA account, will all your certifications/exam history stay linked to personal? I think so, but better to double check with support moderator as described later in this answer.
Have you linked personal account yet to your Learn profile? Below is link, navigate to it and then scroll down to Account management section -- Add account:
https://learn.microsoft.com/en-us/users/me/settings
My personal preference would be to schedule exam while signed in using MSA account, using personal email address, and Learn email notifications sent to same personal email. If that meant canceling and re-booking using MSA and different email I would do it, but that is just me. Cancel/rebook can cause complications in some cases because you may have used discount voucher.
Exam/certification questions are handled by the support moderators in the Microsoft Credentials forum. Please use link below to ask your question over there. They typically respond within 2 business days.
https://trainingsupport.microsoft.com/en-us/newthread?threadtype=Questions&forum=mcp
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP