Hi @izzets6586254,
Thanks for sharing the screenshot. I can see how frustrating it is when white graphics blend into the preview background in the Libraries panel. Right now there isn't an option to change the preview background, which is why transparent white artwork ends up looking like a solid white block. A workaround for now is to place the asset on an artboard or a darker background in Illustrator, so it's easier to spot.
I understand how important this functionality is for your workflow. It would be great if you could add your request here: https://adobe.ly/4nziq9D. Submitting it there helps the team prioritize the improvement, and you'll also get notified when there are updates.
Best,
Abhishek