If not empty, a DefaultMenu will be added to store and reselecte values of the entry easily. These default values are stored by the Defaults system as type app. The default option gives the key for getting and setting values. Label text to be displayed in the entry label. If this is empty, no label will bne displayed.
Command associate a command with the entry.
The command will be executed in global scope. If you want to use temporary variables without poluting the global namesspace, the Extral invoke command might interest you. Constraint the value in the entry must match the regular expression given here. No constraint is applied when it is set to the empty string. This is a more general method to do validation of the entered value.