Use 'For a selected item' on a file

I was interested in your issue, so found a solution that works for me. I did not use the "For a selected item" but started with going to the library, selected one file and choose "Create a flow".

This loads several templates, I choose "Post a message to Teams for a selected file" (I could have chosen differently). Use the Continue button - you will now be able to modify the flow.

The first action is "Request" - ignore that one, it is as it needs to be.

The second action is "Get item" - ignore that one, also good as is.

The third action is "Post message 2" - delete it!

Now you can add your third action as needed and do whatever you want with the item/file.

When you save the flow, and returns to the library, you will observe that when you select a file and looks under flow, you will see your flow's name there. :)

Hope this helps you on the way!

Kind regards

John