In DataFlex 19.1 we introduced 'history management' which basically made the back button work. Part of this is that al the possible navigation paths need to be registered. See the documentation links below for an explanation.

https://docs.dataaccess.com/dataflex...Management.htm
https://docs.dataaccess.com/dataflex...th_command.htm

Note that you can turn this off by changing the peApplicationStateMode:
https://docs.dataaccess.com/dataflex...nStateMode.htm