Error List
The Error List tab is only active after a compile error occurs (See the figure here). Compile errors are generally rare, and we request that you send any pXMLs which do not properly compile by opening a support ticket for analysis.

The figure shown. A Endpoint Policy Manager DesignStudio compile error.
When errors do occur, the error list pops up and suggests some fixes, as shown In the figure shown. Double-click the proposed fix (or right-click and select "Apply Default Fix") for any errors found, as shown In the figure shown.

The figure shown. Applying the default fix to errors.
If the errors are not corrected, send Endpoint Policy Manager technical support your pXML file for analysis and a fix. We want to help! Please open a support ticket.