Today I had a look at the button options in Microsoft Flow.
I created a flow with Manually trigger a flow trigger with just one input field of the type File content. You could even add more input fields here. So that you could ask for related information that you might want to ask the user for. Imagine for example if you created an expenses submission solution. You could ask for the name of the project related to the expenses or anything like that.
In my case I just wanted to upload a photo of last night’s PowerApps and Microsoft Flow user group
I hit the Share button to share my photo and an option to Share with Flow now appears on my phone.
Now I get a file import screen. This is where you will also find the additional fields if you were to ask for more fields in your Manually trigger a Flow trigger
Once I click on Done, my file is uploaded to SharePoint.