Hi golem1138,
We understand you are missing the scroll bar when using Numbers. We want to help get this resolved. To start, we recommend checking some settings for the scrollbar:
If using macOS Monterey, choose Apple menu > System Preferences, then click Displays. Click Display Settings, then select your iPad in the sidebar.
If using macOS Big Sur or macOS Catalina, choose Apple menu > System Preferences, then click Sidecar.
These settings are available only on computers that support Sidecar.
• Show Sidebar: Show the sidebar on the left or right side of your iPad screen, or turn it off.
• Show Touch Bar: Show the Touch Bar on the bottom or top of your iPad screen, or turn it off.
See more about that here: Use an iPad as a second display for a Mac - Apple Support
If this issue continues, let us know if you're only seeing this happening when using Numbers or if it happens in other apps as well.
Thanks.