Allow "Manual close" option is greyed out if triggers are creating automatically from trigger prototype and from default template. Tested with windows default OS template. the services are discovered automatically by the default template and trigger prototypes are created automatically. But unable to check the option "manual close the trigger" in such cases.
if we manually create a new tigger prototype or new trigger, there is no such problem and able to check "allow manual close"
seems like its a bug. Please check.