This problem still applies to the current Version of Camtasia Studio v8.4.
Last year I inserted a bullet list from Word 2010 into a Text call-out.
While in Camtasia v8.3 the text looked perfectly alright, something has changed due to the update in v8.4. The line height has changed. And I just can't change line-height or anything similar now in Camtasia Studio.
I very much like to suggest to improve the Camtasia Studio Rich Text text editor for call-outs.
Microsoft provides a RichTextBox control for free - possibly that's what Camtasia Studio is already using for the Text call-out. You'd just have to add the corresponding toolbar items.