Short story:
Today, when device finds new VO2max, it uploads new value to Garmin Connect.
If the value is wrong, for example when the device was reset, I can manually edit VO2max value in Garmin connect, but it is not synchronized back to device(s).
Long story:
My wife stepped on Garmin Index scale, which identified her as me, the weight was synced to Garmin connect, from where it was synced to my Fenix 5x. So during my next training sesion, my VO2max skyrocketed. After finding out I did not become the new Brownlee overnight, I adjusted the weight and VO2max manually in Garmin Connect. The weight then synchronized to Fenix 5x but the VO2max did not. And it sits there with too high value for over a month of trainings and does not drop. So my every trainig starts with "Form - below average" message, which is a bit frustrating.