The Shape Data (nee Custom Properties) dialog and window only provides a single line to view or edit text values. It is a great shame because the value can be up to 64k characters, and long text can be pasted into it. I, and many others, have complained about this for many years to Microsoft, but nothing has been done to rectify this. Of course, I do develop custom user interface components for many customers, but that is not always desirable. Therefore I sometimes re-purpose standard Visio elements to provide the ability to view or edit multi-line text in Shape Data rows.