Hello,
This is unfortunately not something you have the opportunity to do OOTB.
ServiceNow had this up for discussion far back in time, and it was talked about that this was something that would be included in the platform.
Considering the current focus on Flow designer, I unfortunately do not think this is something you can hope for.
Unsure if there is any functionality for this on the Store, but it may be worth a try to look. ServiceNow Store.
If you would be interested in trying to build this on your own, then a combination of these two could be relevant:
Automatically create process diagrams in Visio from Excel data
Exporting Graphical Workflows in One Step
