How to create Collapse and Expand section in InfoPath

• Create an InfoPath form as shown below.
• Add a section to this form.

• Add two buttons ( Expand & Collapse symbols). 

• Now create a column ( Flag) of Boolean type. It will have value 0 or 1. Set default value as "1".
• Write the rules on two buttons ( Expand & Collapse) for setting the values of flag column. On "Expand(+)", set value to 1 and on "collapse(-)", set value to 0.

• And also write rule for display either one at a time. Means if one is button displaying another should be hidden.

• On "Expand(+)", set flag to 1 and on "collapse(-)", set flag to 0.

• Finally for the section to collapse or expand, write an action on the section. If Flag = 0, hide the section.