using anchor to change a variable

You should be able to format all your links like this:

MyPage.cfm
---------------------
<cfparam name="bShowSection" default="">
<a href="myPage.cfm?bShowSection=first_section">+</a> First Section
<cfif URL.bShowSection eq "first_section">
<!--- process code, include file, run query, etc --->
</cfif>

You could also use JavaScript to control your show/hide functionality, which would be much quicker response-wise, but would require you generate the code for all your expanded sections at once.

I'm creating a table with subtables that can be included by clicking a (+) on expandable areas. I figured if I toggled a boolean var, when a plus (or minus), was clicked the page would be refreshed with the table displaying the new query depending on which vars were set to true or false.

It sounds like Dan's suggestion is your best bet - you can even link to the same page, passing a URL variable at the end of the link that you can use to change your CF variable:

myPage.cfm
<cfparam name="myVarA" defalut="B">
<cfif isDefined("URL.myVar1")>
<cfset myVarA = URL.myVar1>
</cfif>

<cfoutput>
<a href="myPage.cfm?myVar1=foo">#myVarA #</a>
</cfoutput>

Can you tell us a little more about what you're trying to accomplish? There may be a better solution to your problem.

Link the anchor tag to another cf page and change the variable there.

iframes might be helpful. More helpful than the preceding paragraph in fact.