To do Hide/Show Buttons - you must have a Plus account (the ad-free K-12 teachers is good)

Step 1: ONCE ONLY
Go to: Manage Wiki -> Look and Feel - > Theme -> Edit (You may need to make a NewTheme)
Directly after the line: <style type="text/css">
Add: (I actually have about 30 such lines - you use these if you want to start with "hide"; use any other number if you want to start with "show")

#div1 {
display:none
}
#div2 {
display:none
}
#div3 {
display:none
}
#div4 {
display:none
}
#div5 {
display:none
}

Click on: Save

Step 2: ON EVERY PAGE THAT YOU WANT SHOW/HIDE (unless you have pro version)
Open this page for EDIT
---
Open the widget below, click in the field and do Ctrl+A, Ctrl+C

Open your page for EDIT
Enter a couple of times.
Click on Widget and Click on Other HTML
Click in the field, do Ctrl+V
Click on: Save
YOU CANNOT COPY A WIDGET - you must copy the contents.
This widget will NOT show on the page! It is the javascript function for show/hide

Step 3: In your HTML for you page for a section you want hidden on load

<input type='button' value='+' onclick="showHide('div1','hide','+','-','')" />
Text Next to Button HERE
<div id="div1">
What opens here
</div>

Here is the Widget with Other HTML here with exactly the above code (open it):
Text Next to Button HERE
What opens here