Yes, you can share personal contacts to Secure Folder or vice versa. Go to Secure Folder > Settings > Notification and data > Contact and calendar

1. Import to Secure Folder: Contact and calendar from outside container will be shown inside Secure Folder
2. Export from Secure Folder: Contact or calendar of Secure Folder will be shown outside Secure Folder. (Contact and Calendar app outside Secure Folder)

*Please note, this menu is only available on the devices where Secure Folder is preloaded (e.g. Galaxy S8).

See the Secure Folder User guide for more information on using Secure Folder.