Horizontal toolbar resizing vertically when thumbnail slider shows

Am trying to stop the horizontal toolbar from resizing and re-positioning icons as much as possible.
Can be a bit distracting seeing it move in peripheral vision.
The thumbnail slider is on the toolbar and when it shows the toolbar will resize vertically because the size of the icons is not the standard 32px (they are 26px).

Possible solutions :

  • have the thumbnail slider always showing
  • have the thumbnail slider size itself to fit largest icon size on toolbar
  • allow user to set vertical height of thumbnail slider in it's settings

what do you think ?

I don't think the slider can be any shorter without rendering incorrectly. (It's a standard Windows control.)

How about having an option to always show it ?
Is there an argument that will do this for the thumbnail slider ?
(Just disable it when not in thumbnails mode.)