Challenge 1: Combining 12 Monthly CSV Files Automatically — Solution Walkthrough

The correct Get Data option: From Folder.

Steps:
  1. Data > Get Data > From File > From Folder.
  2. Point it at the folder containing the 12 monthly CSV files.
  3. Power Query lists every file found in the folder, then offers a
     "Combine & Transform" option that opens all of them through the
     same cleaning steps and stacks their rows together into one
     single table (an Append happening automatically behind the
     scenes, once per file).
  4. Close & Load the combined result.

What happens after a 13th monthly file is added and the query is refreshed:

Because "From Folder" doesn't reference the 12 original files
individually by name — it references the FOLDER itself, and combines
whatever files are currently inside it — refreshing the query after
adding a 13th file automatically picks it up and includes its rows in
the combined result too, with zero changes needed to the query
itself. The same recorded cleaning steps (data type changes, any
renaming, etc.) are simply applied to the 13th file exactly as they
were to the first 12.

Explanation:

This is the genuinely powerful part of From Folder that a manual
"import each file separately and paste them together" approach could
never replicate automatically: the query describes a PROCESS ("take
whatever CSV files are in this folder, clean them this way, stack
them together"), not a fixed list of 12 specific files. A growing
folder of monthly exports is exactly the situation this feature is
built for.

Notes:
- This only works cleanly if new files keep the exact same column
  names and layout as the original 12 — this chapter's own warning
  box about a renamed source column breaking recorded steps applies
  here too, just at the file level instead of the column level.