How to reuse PQ transformation steps or create a PQ template?

You can create a custom function. But if you are really new, start here: https://learn.microsoft.com/en-us/powerquery-m/understanding-power-query-m-functions

It is not really hard if you have some coding experience.

The UI also gives some support.

If you want a solution, you could post the query here for someone to convert to a function.

I don't have access to my laptop at the moment, so it will have to be someone else...

You could just open yesterday's workbook with the query that you used, and change the Source to the newest file. Then all of your steps will apply to the new file. 

--Nate