This dialog is available from the Graphs / Options / Overlaid Portfolios... menu command.
This dialog box allows you to select the portfolios that will be overlaid for the Portfolio/Investment(s) Overlay graph types. Highlight the portfolios to overlay. The "Clear All" button deselects all portfolios. The "Reference Portfolio" is used for calculating the hypothetical value for each overlaid investment in the Portfolio / Investment(s) Overlay - Value" graph type.
This dialog box selects which portfolios to overlay. To actually overlay the portfolios you must select one of the "Portfolio/Investment(s) Overlay" graph types from the Graphs menu.
Selecting Investment to Overlay