Breath and pause markings are available in the Breaths & Pauses palette (Advanced workspace).
To add a breath, or pause (aka caesura / "tram lines" / "railroad tracks") to the score, use one of the following options:
The symbol is placed after the note. Its position can be adjusted by editing the X and Y offsets in the Inspector, or, in edit mode, using the arrow keys.
You can adjust the pause length (in seconds) of the added symbol in the Inspector.