If you would like to select and match the amount of measures in a system or stave, please do the following:
Select the tab "Home"
Select the tab "Palettes"
Mark the stave, using a simple left click.
The menu "Layout Properties" opens.
Select the tab "System"
Enter the amount of measures per system or the amount of systems per page.
Click "Apply" to confirm your selection.
These options are applicable to any selected system on your page.