for example when i use ExpertMACD demo from MT 5.0 its posiible to change the parameters of MACD indicator from this EA based on Standard Library? How to do this on-the-fly?
Lol, then your opinion is rather different from the one of a bug fixer:
There is incorrect reset. After the command. all indicators attached to the chart reset properly, but the one that calls the command.
Right after the command it calls OnDenit, OnInit (so far good), but then it returns to a command following the original ChartSetSymbolPeriod and continues the method. There are no valid objects any longer, so it mostly ends in invalid pointer error.
My request to service desk was about disabling this return.
My suggestion is - you may still use the command, but with caution that it is the last command in the event method.