Prior to creating a map with queries I was able to add fields and edit fields associated with the layers and tables through the DATA tab (see attached image). Now that I've created the maps, this edit option is no longer available. What should be done to restore the option to edit /add fields?
it appears as if your username does not have appropriate permissions to alter the data.
With appropriate permissions, you not only can modify the table, you will also see the Settings tab in the upper right.
Someone with appropriate permissions will have to change/reset the permissions for that hosted layer.