You can include ossia staves in, or exclude them from, the preamble when they cross system/frame breaks in each layout independently.
Showing ossia staves in the fixed preamble means their clefs and time signatures appear alongside all the regular staves at the start of each system. As this can suggest the ossia staff is an additional instrument, it is common to exclude ossia staves from the fixed preamble.
Procedure
Press Ctrl/Cmd-Shift-L to open Layout Options.
In the Layouts list, select the layouts in which you want to hide/show ossia staves in the preamble.
By default, the layout currently open in the music area is selected when you open the dialog. You can select other layouts by using the selection options in the action bar, clicking and dragging across multiple layouts, Shift-clicking adjacent layouts, and Ctrl/Cmd-clicking individual layouts.
In the category list, click Staves and Systems.
In the Ossias and Extra Staves section, choose one of the following options for Ossias crossing a system break:
Include in preamble
Exclude from preamble
Click Apply, then Close.
Result
Preamble notations for ossia staves are hidden in the main preamble in the selected layouts when you choose Exclude from preamble, and shown when you choose Include in preamble.
