This setting is a boolean setting. It specifies whether a heading or plug-in parameter is initially expanded when the formula is selected. It defaults to true, so you only need to include it when you want a heading or plug-in parameter to be collapsed by default.
If you want your formula to run on version 3 or earlier of Ultra Fractal where the expanded setting was not available, test for the VER40 symbol, as shown in the example below.
default: heading caption = "Additional Options" $ifdef VER40 ; Hide these options because most people won't need them. expanded = false $endif endheading ; Declaration of optional parameters