Scale Length and Distance to Full Range
The Scale Length and Distance to Full Range command can be found in the Options menu at the upper right of the Flex Projection panel. It scales the lengths of parallels and the distance of parallels from the equator to their full range, i.e. if the largest length value is smaller than 1, all values are scale such that the largest value is 1.
It is recommended to use this command at the end of the design of a new projection.