A frequent issue, something that is evident in both 2011 & 2013, is the ‘add new and add existing’ buttons on the ribbon bar on certain entities (normally new customised ones) and getting rid of these as it causes confusion for clients, especially when they will to ‘add existing’ only to select one and be notified it has already got a parent.
A specific 2013 issue that comes with this is when using subgrids on related entities, you’ll find there is a selectable ‘+’ mark which opens up the search bar in the subgrid rather than making a new record. This functionality is also due to the ‘add existing’ button being available from the navigation bar
To get rid of these buttons, without going into the ribbon editor or using any code, is to make the related field, depending on which side of the relationship you want to remove, business required.*.
In this example, I’ve created a new ‘Project’ entity, and associated it to the ‘Account’ oob entity. I’ve added the ‘Account’ lookup to the Project form, and the Account forms have the ‘Project’ navigation rectangle on it.
I’ve made the Account lookup, which is the side of the relationship I want to edit, (think of it as ‘where am I sitting?’ – on the Account, or the Project? In this case I’m sitting at the Account only wanting to add new Projects, so if i make the related relationship lookup on the Project Mandatory, I can not save a record that is not associated to an account, and therefore the ‘Add Existing’ button becomes useless, thus, disappearing.)
Below, you can see the ‘Add Existing’ button has now disappeared.