Issue Description
You have just created a lovely 3D view ready to render but you realize each opening element is showing an opening line ruining the look of the image
Solution
In the Model View Options Dialog, go to the "Miscellaneous Settings for Library Parts" panel. Use these controls to set the display of Opening Lines for each opening type, Door Window, or object. Uncheck the checkbox in the "Show Opening Line in 3D" field. to remove the lines.
Please note:
Since this is an MVO setting, it is stored with the view, if it's not saved, it may change when another View is activated.