It isn't currently possible to create or set properties as private for individual users in Hubspot. Properties are only specific to portals. I encourage you to post this as a suggestion on the Hubspot Ideas Forum. Our product teams look through the forum to see what our customers are requesting and if they find that an idea is feasible, scalable, and highly sought after, they do their best to work it into a future product release.
It isn't currently possible to create or set properties as private for individual users in Hubspot. Properties are only specific to portals. I encourage you to post this as a suggestion on the Hubspot Ideas Forum. Our product teams look through the forum to see what our customers are requesting and if they find that an idea is feasible, scalable, and highly sought after, they do their best to work it into a future product release.