Hi @SherryeBiglow
I'm going to point you to this discussion where your question has been partially answered by @Chris_Hofer
https://community.canvaslms.com/t5/Canvas-Question-Forum/Can-you-add-a-status-in-gradebook-for-assig...
As to why there are only missing/late/excused, I believe it has to do with the status being more than colors used to identify missing/late/excused assignments. They are actually designed to be used by instructors to to control what and how grades are calculated for a final grade. You can use the gradebook settings to deduct points for late assignments, choose to assign zero points for missing assignments, and excuse an assignment (it won't count for the student's final grade).