Keep the edit header sticky with a solid background

[rfontanarosa]

closes #2514

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.54%. Comparing base (c759b97) to head (eae40e2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2561   +/-   ##
=======================================
  Coverage   62.54%   62.54%           
=======================================
  Files         119      119           
  Lines        2878     2878           
  Branches      432      432           
=======================================
  Hits         1800     1800           
  Misses       1016     1016           
  Partials       62       62           

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