I mean what for the window FIR filter the filtered signal is truncated at the end because impulse response of the filter is symmetric. For example the code from here (in python) (lowpass FIR filter) gives the next results:
blue - input signal
green - shifted filtered signal
red arrow - the end of the filtered signal
The red arrow shows where the filtered signal is ended. How can I implement the zero - phase or nearly zero - phase filter so what the filtered signal would end at the same point in time as the original one? The end of the filtered signal is of most significance.