Variables in "Locals and Expressions" panel change their listing order when starting a new debugging session or when modifying a variable name

I'm developing a C++ program
I experienced this problem:

• I added some custom variable in the "Locals and Expressions" panel
  In detail it was something like:
  pnodo2->el.x
  pnodo2->el.y
  pnodo2->el.r
  pnodo2->el.end
  pnodo3->el.x
  pnodo3->el.y
  pnodo3->el.r
  pnodo3->el.end
  everything OK

• then I quit the debugger and start it again: the listed variables changed their order in a incomprehensible way, becoming:
  pnodo2->el.end
  pnodo3->el.y
  pnodo2->el.y
  pnodo3->el.x
  pnodo2->el.x
  pnodo3->el.r
  pnodo3->el.end
  pnodo2->el.r

This is quite annoying... because every time I need to cancel and re-write all the variables