MuseScore -- Index -- Bar Line

Change bar line type
Bar lines are changed by dragging a bar line symbol from the bar line palette to an bar line in the score. Bar Line palette
Create grand staff
To extend bar lines over multiple staves double click on a bar line to edit it (see Edit mode ). Bar Line edit mode
Click and drag the blue square down to the next staff. All staff bar lines will be updated when you leave edit mode . Grand staff

See also Measure Operations.