Link to page and screenshot showing the thumbnail compared to the others?

Thanks, it worked: by inserting the logo image, instead of the full name of the site, you get the button with the transparent background

While on the site, you can click the heart icon and use the left and right arrows to pic a different thumbnail.

Or, you can right-click a speed dial and choose to change its image to a different pic that you download.

Thanks for your reply, but that's not what I need. I just want the background of the new button I added to be transparent, like all the others, and not white like it is now...

Or, you can right-click a speed dial and choose to change its image to a different pic that you download.