Excel file name as custom column - append current query with new data

Greetings!

I have several files in different locations that are the same data pulls (perhaps with a few variations) but are from different years. After many steps on the query editor, I have shaped my data the way I want. Now 2 things:

1. Is there a way to have a custom column that would display the file name of the excel document? The files all follow the same naming convention where the year precedes the file name (ex. 2018_filename) . Is there a way to add a custom column to my orginial query that will display the file name? (Even better if there is a way for only the year of the file name to show!)

2. How do I append my current query with my other files where they will go thru all the steps my orignial file had to undergo? When I tried to add a new data source in the Home tab of the query editor, it created a new query instead of appending it to the query I was working on. 

I am very new to PowerBI and appericate all help!