A family of Microsoft relational database management systems designed for ease of use.
viziblr - News - Visio – Creating Double-Lined Shapes
John...
I read that article before asking here. Tell me first how do you open the Line dialog in Visio 2019. Also, there is no "Double line" option in Format Shape pane.
Always read the question in full first, understand it, and then check your answer to make sure it is correct and to-the-point before submitting. I believe this is the basic requirement to a person with title "MVP".