Help Configuring - Default Flow & File naming

First let me say - Totally new to Flowable but trying to learn “How”. I have spent the day searching for two things with no success.

When creating a new flow - my exclusive gateway option Default flow : doesn’t seem to be enabled to allow for setting the flow as the “default”. What am I doing wrong??

Next the file(s) are saved as [flow name].bpmn20.xml – Is there anyway to configure a change to save the file(s) as [flow name].bpmn

Thank you in advance for any/all help…