Fixed stationary event handler editor window

[Patrykb0802]

Problem description:
When using bigger configuration ( >2000 data points), at event handler view when trying to edit event handlers, the editing window is stationary, after scrolling down and choosing suitable event you have to scroll back up to edit it.
Describe the solution you'd like
Appropriate solution would be to "glue" event handler editing window to top border of browser window same as in data point/source view. That will greatly improve ergonomics.