Manually changing stem direction

Muse Score doesn't seem to want to allow me to change the direction of stems when writing for piano using treble and bass clef gereat staff. For example, writing a quarter note (crotchet) melodic line in an upper part (with stems up) and half notes below with stems down, all to be played by the right hand. Muse Score seems to want me to write everything in quarter notes and then use ties for the lower part. Similarly, the sort of manual manipulation of stem direction that I'm talking about is also essential in all contrapuntal writing for the piano to show the contrapuntal direction of each part. Anyone out there got advice on this topic?