This User Specific Setting sets whether the user can add columns (i.e. insert variables, list inputs, etc...) when using a Monthly Data Entry Form. If checked it does NOT mean the user can save the layout changes (use Entry Forms Group Manager to specify whether a user can save design changes).
With this setting off, if a user tries to List Inputs, add column, etc.. they will receive the following message:
"You do not have Add Column privileges (User Setting) to access this feature."
This setting is per Facility. (Key = ADD_COLS_TO_MDE_FacilName)