Attribute not showing up in Attributes Tab of Structure Tab

A Part Attribute "XXX" which I created is of data type : URL/Hyperlink. I added it to the layout "Part Structure Attributes". However, this attribute is not showing up in the Attributes Tab under Structure Tab of a part. 

I want this attribute to show up under the Attribute Tab inside the Structure tab of a part. Other attributes with different data types are showing up in this Attributes tab. The problem is with only this attribute whose data type is a URL/Hyperlink. Please give insights on how to resolve this. Thanks in advance.