In one of my piano compositions the bracket of the piano system is outside of the music frame, in all other piece the bracket is inside. Where I can change this?
The correct position of the brace is outside the frame, i.e. it is expected that the systemic barline should be aligned with the frame edge unless there is a staff label inside it that would prevent that from being the case. It looks to me as if you have edited the name of your piano instrument to be empty, or perhaps just a space, in the score in which the barline is inset from the left-hand edge of the frame.
The need for the brace inside the margin comes when creating a page of numbered examples, some being single staff and some being grand staff. Visually, the space between the number and the staff is better if the grand staff brace lines up with the other single-staff examples.
Other situations would be when a publisher requests the brace to be inside the margin, so that nothing is printed in the margin.
There are work-arounds, but it would be helpful to be able to choose this option, depending on the music.