Let the Layers panel show a small thumbnail preview for each layer
In a file with many layers I often lose track of which layer holds which artwork, because the Layers panel only shows names. A small thumbnail preview next to each layer name would let me find the right layer at a glance without expanding or selecting each one. This would be especially helpful in complex illustrations with dozens of similar-looking layers, and it would save a lot of clicking around.
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Illustrator shows thumbnails for the layers in the Layers panel, actually. 'Medium' by default, but you can change it to 'Large' or use your own size, in the Layer Panel Options dialog, available via Layers panel’s flyout menu (the ’Panel Options...' item at the very bottom of it). Does it work for you?