mom2boys,
I guess it depends on what writing software would provide you. If you were writing scripts, for example, it may offer formats and templates for the script to be written in and submitted.
I read a string in this forum where you want to write children's books. Really, I should think that a word processing program would be sufficent. With just about any program you can set margins, font type and size, underline or italicize as needed, proper spacing etc.
I guess there are software programs out there that help develop a plot, track story plot lines, random character development suggestions, etc...but how useful would they be? I strongly suspect that they would not be very helpful. Anything input by the software designer is going to be generic and would probably do nothing more than give general promts and ideas for you to build from.
I would get a good book on writing children's literature, maybe even from the Library. The only one I have heard of that might be moderately useful is: You can Write Children's Books by Tracey E. Dils. But really, I've never even considered writing children's books. Those who have considered, tried and written, may better be able to direct you to useful/effective resources.
Just one opinion.
R-Tech