it seems that adding the keyboard shortcuts for navigating in ProofreadPage T186478 completely destroyed the possibility of using the editTools and toolbar on Page ns. See: New_problem_with_the_special_characters_toolbar
Please provide steps to reproduce the problem so someone else could follow those steps and see the same problem - see https://mediawiki.org/wiki/How_to_report_a_bug - thanks!
Thank you for the bug report. It's definitely not the introduction of rel=prev/next that introduced this problem but something else. See T187454
Thank you @Tpt