Expression Manager organizes all your common SSIS expressions which you can use with variables, control flow tasks or Data Flow pipeline.
All user defined expressions are listed under "My Expression" node on the expression editor (While editing variable/task expressions inside BIDS.)
You can re-arrange item nodes easily by dragging under different folder node.
With Expression Manager you can do the following things
• Create new expressions and define Title, Description and Syntax (i.e. Expression)
• Delete Expression
• Add/Delete Folders to organize expression in groups
• Change path of User defined expression file. If you want to share expression file with team you can put expression file on network share so other developer can use it.
• View standard expressions in read-only mode (Installed with BI xPress)
You can launch Expression Manager in 3 different ways
• Launch from Variable Toolbar (See folder icon with function image).
• Launch from main application window.
• Launch from expression editor by clicking expression manager icon.
Expression List Add-in automatically lists all expressions for any SSIS objects so you can easily edit them with "Single Click" Edit option. By default Expressions are refreshed automatically when you add/delete or rename various SSIS objects. To turn on/off automatic refresh you can use "Auto Refresh List" option found on expressions window (If Expression window is not visible then click the expression icon  on the toolbar).
Use "Enter" key to edit selected expression