I had a second thought.
To get some hierarchy, create a tiddler "Categories". Give it a field "list" containing a list of your Categories. In the example it would only contain "Medical" (without the quotes).
Give the "Medical" tiddler a field "list" containing the sub categories. So in your example "[[Name of Condition 1]] [[Name of Condition 2]]" (without the quotes! The brackets are required as the sub categories contain blanks,)
Give the "Name of Condition 1" tiddler a field "list" containing its sub categories "Treatment Specialist" (without... You already know)
Give the "Name of Condition 2" tiddler a field "list" containing its sub category "Documentation"
Create an overview tiddler like so:
<$list filter="[list[Categories]]">
! <$link><<currentTiddler>></$link>
<$list filter="[list[]]">
!! <$link><<currentTiddler>></$link>
<$list filter="[list[]]">
!!!<$link><<currentTiddler>></$link>
</$list>
</$list>
</$list>