With GUI Scale Auto and 1920×1080 screen, the toggle bookmarks icon renders very badly compared to the options icon:

Instead I propose you use these not up-scaled:

16×16 pixels icons:

Compared to the current borked pre-scaling, these would scale as fairly as the wrench option icon:

If this persists after the next beta please let me know, or swap out the assets on nei_tabbed_sprites.png