This is
#1184. Imo, an equal-sized-
panes command makes little or no sense when using docks. How is the code to know the present layout?
This post discusses the equal-sized-editors command.
Recent code used QDockWidget.setFixedWidth() to do the job, but this is way bad. It becomes impossible to move the editor docks! Furthermore, the editor docks are too big. Any "adjustments" would just be hacks.
This looks like a surprisingly tricky enterprise. One possibility would be to replace the layout manager that contains the body editors, but this might have side effects because Qt is already managing the dock widgets.
In short, it may be awhile...
Edward