Add a field to account

[maciej.pioro]

Hi,
I am looking for a way to add some fields (attributes?) to Zimbra accounts. Those fields (a boolean value and a date) could only be set by admin in the admin console, along with other fields such as name or address.
Admin should also be able to view (perhaps a sortable list view) accounts for which the boolean is true.
I found that this tutorial achieves a similar effect: https://wiki.zimbra.com/wiki/Domain_Dis ... n_Admin_UI but it seems it's outdated.
If I understand correctly, modifying Zimbra schema is not recommended anymore. How would I approach adding those fields along with interface to change them in Zimbra 8?