Edit Mail Subject
  Get/Send-Button
  Google Search for TB
  Lightning
  More Functions for Address Book
  Signature Switch

With Mac OS 10.13.2 and TB 55.5.2 using high-contrast Charcoal theme, Theme Font & Size Changer v. 62.0 does not work at all, rendering TB unusable for me. Suddenly, without my having changed anything, when TB opens windows, they appear momentarily with a thick black-line border on the sides (but not in the corners) around a white interior, and then the actual content renders and the border disappears. Shortly after that, Theme Font & Size Changer (version 56 something) no longer functioned. I have tried all the usual routines, re-launching, re-booting, re-installing the Add-on, updating the Add-on, re-installing TB... all to no avail. My other Add-ons are: Edit Mail Subject Get/Send-Button Google Search for TB Lightning More Functions for Address Book Signature Switch None of these have changed for months, with no changes shortly before the behavior described above. Nor did they start upon OS upgrade. Any thoughts on what's this all about?