bkbarton on "Adding custom input and linking to page sidebar"

I must be missing something...

Is there a way to...

• have a page template
• that has a 'custom' text input area in admin
• that then passes this 'custom' text to the associated page sidebar
• ...meaning, this 'custom' text will not be visible anywhere else, but the specific associated page it was meant to accompany

In my research, I have ways of adding custom meta data or links or images or to the sidebar of a page... but no way of adding associated content that matches that of the main post. The WordPress community has to have come up with someway of including this content. It is a content management system, right?

Please show me what I'm missing...

Thanks.