I installed with full administrator privileges.

There is no folder named:
"C:\Users\<<user>>\AppData\Roaming\eTeks\Sweet Home 3D\plugins"

I found these eTeks related folders:

"C:\Users\PowerUser\eTeks" (EMPTY)
"C:\Users\PowerUser\eTeks\Sweet Home 3D\recovery" (EMPTY)

All the subfolders in this parent folder are EMPTY:

"C:\Users\PowerUser\AppData\Local\Packages\eTeks.SweetHome3D_y7v7etvrysvmm"
"C:\Users\PowerUser\AppData\Local\Packages\eTeks.SweetHome3D_y7v7etvrysvmm\AppData"

I first did a portable installation of the free version (from SourceForge), and then I installed the version from the Microsoft Store, and I cannot (yet) find where the Microsoft Store version is installed. I hate using the Windows Store because it hides things away from users.

After the Microsoft Store installer, I am still not able to install the plugins, because I cannot find the plugin directory.

By the way, "native" format means the file format(s) that are native to an application, e.g., sh3d for SweetHome 3D, xlsx for MS-Excel, docx and doc for MS-Word. These are also the file extensions that get registered by the Windows operating system in the Windows Registry.

Is there a way to download the "Pro" (paid) version and install it manually without using the Windows Store?