You can modify the way the thumbnails look in the Layers panel. When I’m teaching, I like to make the thumbnails big so everyone in the room can see them. When I’m working on a complex image with hundreds of layers, I like to make the thumbnails small or hide them altogether so that many more layers can be seen at once. Click on the top-right flyout menu in the Layers panel and choose Panel Options near the bottom. You’ll see that you can make the thumbnails small, medium, large or non-existent.
This tip previously appeared in Colin Smith’s Photoshop Tips column, in the April, 2019 issue of Photoshop User magazine.