I had this requirement lately and the first time I heard this I thought, is this even possible? But then I never doubt about the every increasing capability of canvas apps. So decided to do a search.
And guess what! Found this wonderful documentation here with a complete solution.
I am simply falling in love with PowerApps documentation which is so much focused on implementation and solutions rather than just theory.
Towards the end of the solution, you will find a link to download the powerapps solution sample. Link – https://github.com/microsoft/powerapps-tools/blob/master/Apps/BusinessProcessFlow/BPF_Solution_1_0_0_11.zip
One point to note here – The BPF Component shown in the blog is not an OOB control available but in fact it is a generic control custom built for designing a BPF. So if you are searching a control with that name in your powerapps component list, you may not get it.
Hope this small tip helps!
Business solutions MVP