Reproduction steps:
1. Open the attached "PROJECTFILE" project
2. Open the “Assets/Scenes/SampleScene.unity“ scene
2. Select the "SpriteTest" GameObject in the Hierarchy window
3. In the Inspector window, observe the visual variant selector thumbnails located in the Sprite Resolver Component
4. Unfocus from the Unity Editor application to desktop and wait for about 2 minutes
5. Focus on the Unity Editor
6. In the Inspector window, observe the visual variant selector thumbnails in the Sprite Resolver Component

Expected result: Nothing changes and the visual variant selector thumbnails are visible
Actual result: The visual variant selector thumbnails become invisible

Reproducible with: 7.0.11 (2021.3.30f1), 9.0.3 (2022.3.9f1), 10.0.2 (2023.1.13f1, 2023.2.0b9, 2023.3.0a5)

Reproducible on: macOS 13.4.1 (M1 Max)
Not reproducible on: No other environment tested

Note:
- Issue reproduction is inconsistent
- The visual variant selector thumbnails in the Sprite Resolver component disappear once, after the thumbnails reappear couldn't reproduce the issue again, only after restarting the Editor
- The Sprite Resolver visual variant selector thumbnails may disappear when saving the project, pressing the Sprite Resolver component drop-down button