Merging 8.x 1.x dev to 8.x-1.x for 3rd Release Candidate

[8.x-1.0-rc3] - 2021-02-11

Fixed

• Issue #3196330 by quondam: Uncaught ReferenceError: value is not defined
• Issue #3196569 by quondam: TypeError: Argument 1 passed to Drupal\tb_megamenu\TBMegaMenuBuilder::editColumnConfig() causes site crash
• Issue #3195480 by quondam: Improve messaging in toolbox admin UI