Hi  !

I assume that you are referring to the 'plus sign' (?)

Reducing it's size is (as far as I know) not possible, but you could remove it with userChrome.css code

  /* remove New Tab button */
  .tabs-newtab-button {display:none !important;}

Then, to open a new tab, you could just press 'Ctrl + T'

Can you attach a screenshot?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot