Microsoft took a big step forward when integrating Flow into SharePoint-Lists by allowing us to execute a flow on an existing SharePoint ListItem or Document.
However, if you try to create a flow on a document by executing the following steps, the dropdown only shows Lists and no Libraries:
So this dropdown is missing all the existing libraries and shows only Lists. Does this mean, that we can create a Flow on an existing ListItem only? No! There is one thing you need to do – and it's not "enter custom value" with the Library Title – this doesn't work, the Flow doesn't get bound to the Library in this case.
How do you find out the ID of your Document Library? Just go to "Library Settings" and you'll see the ID – without %7B and %7D:
Now you should be able to work with your Document in the Flow – and the Flow gets bound to the Library:
My thoughts and findings about SharePoint 2016/2013/2010 and SQL Server