When you edit database from your site's dashboard, you can add/remove/edit new items but not fields. However, you can add/remove/edit items and fields as well when you edit the database straight from 'Edit Site'.
Now the problem is, because we cannot add/remove/edit fields on dashboard's database menu, you can only edit it from the 'Edit Site'. It does works, but there'll be a catastrophic mistake if you're new enough to unaware how Wix works and Wix doesn't directly tell you how it 'actually' works until your misguided ass fell into Wix fuckery. I'll explain below:
When you edit database from the site's dashboard, each new data will be automatically updated to the 'Live' database. Whereas editing database from 'Edit Site' means you only add the new data on 'Sandbox Collection' and requires you to sync the data manually to update it to your 'Live' database. The 'Live' database doesn't automatically update to 'Sandbox Collection' either and basically you have the same database with two different saves.
Now say, you spend days, or even weeks to months, editing Live database from the dashboard, and decided to add new fields on the database. You'd go to 'Edit Site' database, add new fields and sync to 'Live Database'. Sounds simple huh? But no, that's where you fucked up.
Congrats. You basically just overwrite your Live database with whatever little data left in your Sandbox Collection. Good luck praying to whatever God you remembered because it won't undo your database collection.
This just happened to me so yeah shit, it's depressing. I learned the hard way that the stupidly correct workflow to add/remove/edit fields on existing database is to sync everything from Live to Sandbox first with 'Replace All Items (Live > Sandbox)' sync option, add/remove/edit fields, before finally sync with 'Copy All Items (Sandbox > Live)' option.
Honestly this is just blatantly stupid. There are numerous way to prevent this, like adding more database editing functionality to the 'Live' database editing so users don't need to switch back and forth ; add option to automatically sync 'Live' database to 'Sandbox Collection'; or even better, MAKE 'Database History' feature that's like 'Site History' but for any saved database.
Devs seriously need to take the database development seriously as well, not just the gimmicky graphic templates. I was tempted to purchase Wix Premium at first for the whole easy to use & database functionality, now I feel like I should have learn wordpress instead. :(