New Horizons Save Editor (NHSE) is a save editor tool for Animal Crossing: New Horizons.
It’s a useful tool, but the only drawback is that the devs only provide Windows binaries.
Here’s how to get it running on a Steam Deck (or really any Linux distro).

note: You are expected to do everything in desktop mode if you are using a Steam Deck.

Step 1: Download the NHSE Windows Binaries

1. Go to the berichan.github.io/GetNHSE/.
2. Click “Download Latest NHSE Version”.
3. Extract the zip folder into a directory of your choice.

Step 2: Add NHSE to Steam

1. In Steam, click “Games” -> “Add a Non-Steam Game to My Libary…” (in the application title bar).
2. Click the “Browse” button, navigate to where you extracted NHSE, and select NHSE.WinForms.exe.
3. Find NHSE.WinForms.exe in your Steam library, right click it, and click properties.
4. Click compatibility and check the “Force the use of a specific Steam Play compatibility tool” checkbox.
5. In the dropdown select “Proton Experimental”.

Step 3: Getting the mouse to work

1. Go back to gaming mode
2. Launch NHSE.WindForms.exe from gaming mode
3. Change the controller layout to “mouse only” (one of the default layouts).

You can now launch NHSE directly from Steam.
Keep in mind that you are running a Windows app on Linux, so you might run into some issues.