Hi
In the middle part of my score, I want to move the bar line to appear after the third beat and before the fourth beat, so the fourth beat appears like in an upbeat bar.
I want the music to stay the same, just move a barline. How do I do that? this is in a bar of 4/4 time.
You can insert a barline at any point: select the note before which you want the barline to appear and type Shift+B to open the bars and barlines popover, then enter | or single into the popover and hit Return. More information on creating barlines can be found here.