Runtime Expand / Collapse All option for your SSRS Report

1. Add a new report parameter:
   Name: ExpandCollapseAll
   Data type: Boolean
   Prompt: Expand / Collapse All
   Available values:
   Non-queried
   Label: Collapse All. Value: False.
   Label: Expand All. Value: True.
   Default values:
   Non-queried
   Value: =False.
2. For each Toggle Control Item (item that controls the visibility of another item)
   Right-click item and select Properties
   Select Visibility tab
   Initial appearance of the toggle image for this report item:
   Expression:
   Value: =Parameters!ExpandCollapseAll.Value.
3. For each Toggling Item (item that shows and hides)
   Right-click item and select Properties
   Select Visibility tab
   Initial visibility:
   Expression:
   Value: =Not Parameters!ExpandCollapseAll.Value.
   Check Visibility can be toggled by another report item
   Select the corresponding Toggle Control Item
   Note: "Not" is used in the Toggling Item. Here is a helpful key:
   Toggle Control Item:
   True = Expanded (-)
   False = Collapsed (+)
   Toggling Item:
   True = Hidden
   False = Visible