How can I embed html or an image in a custom form?

In the Solutions menu, the description field has several options such as Bold, Italics, Underline, left justify, center text, insert image, Insert Edit media (allows embed code)

Custom forms do not have this menu.  The description of a custom form appears to only allow unformatted text. 

How can I create a custom form which takes advantage of these features?  How can I insert an image, link, bold text, or html embed code into a custom form?  Is there any other way of editing the html for the default new solutions page?