Add new editor environment for 3D preview

[RachelDfs]

Material Maker version:
1.4a

OS/device including version:
Windows 11

Issue description:
When downloading a new environment for the 3D preview in material maker, using the "Tools" menu --> "Environment editor" --> "Download environment", can't see the downloaded environment.

Steps to reproduce:
Downloading a new environment by clicking the "Tools" menu --> "Environment editor" --> "Download environment" and choose a new one.
The new environment will appear in the list, but will not be able to be selected when you click in the "Environment" --> "Select" menu.