The problem is, you may still have to scroll through several grid screens to find the picture group you're looking for. To cure that problem, all you have to do is designate any group of selected pictures as a stack. The first picture in the selection will be the picture you see in that grid panel. The others will be stacked beneath it. So now the picture you were looking for is represented by one thumbnail that looks like it's sitting atop a stack of slides.

Here's all you have to do to get it that way: In the Grid view, follow the instructions in the first paragraph to drag all the photos into the groups that you want to have in each stack. Then, later, when you expand a stack, they'll all be together. Next, select all the photos and press Cmd/Ctrl + G. All the pictures will be hidden beneath the first picture and you'll see a small number in the upper right corner of the picture.

Now any time you want to see all the pictures in the stack, just tap the letter S. You'll see all the images side-by-side in the grid. You can then seltect any of the individual images in the stack and work on it. You can open and close the stack whenever it feels convenient.

You can also have stacks within stacks. That's important because Lightroom can be asked to automatically stack images that are variants of the same image, such as multiple "exposures" of a RAW file or files that you've done additional processing for in Photoshop. You'll probably want it to work that way. All you have to do is to include that automatically made stack within the stack you make by subject type. When you open the subject-type stack, you'll see the individual stack and you can then open them.