Select a note in the voice that you wish to move up or down to the other staff. e.g.
Press Ctrl+Shift+↓/↑ (Mac: Cmd+Shift+↓/↑), to move the voice up or down to the other staff. Alternatively, you can click on the cross-staff icon in the note input toolbar and choose the same options from the context menu.
Note: This operation works on a voice basis, rather than on individual notes. It follows that if you want to ensure that notes remain on the same staff during the operation, they should be in a different voice to the one selected above. Be aware that notes which have been moved to a different staff still belong logically to the staff of origin. This is why no rest is shown in the place where the moved notes originated.
To adjust the beam angle and height, click on the beam, then click on an adjustment handle and use the keyboard arrows, or drag the handle with a mouse. e.g.
Alternatively you can make more precise adjustments from the beam section of the Properties panel.