I might have a custom module I can share with you to toggle on and off some actions for the basic users,
but lets make sure I get the problem first,
if you could provide a screenshot of what actions you want to disable for 
the basic user (waiter).

1. Create or Link an Employee to a User

1. Go to Employees > Employees.
2. Open the Employee record (e.g., John Doe).
3. Under the Work Information tab:
   • Set the Related User field to the system user account (e.g., john.doe).
   • This links HR Employee to POS login identity.

2. Assign POS Access Rights to the User

• Go to Settings > Users & Companies > Users.
• Open the linked user.
• Enable these access rights:
  • ✅ Point of Sale (User or Manager)
  • ✅ HR Employee (if managing employee-linked roles)

3. Enable Cashier Selection in POS

• Go to Point of Sale > Configuration > Point of Sale.
• Choose your POS (e.g., “Main Restaurant”).
• Under the IoT & Hardware section:
  • ✅ Enable Login with Employees.
  • ✅ Optionally: Set Authorized Employees if you want to restrict.

4. Assign PIN Codes (Optional)

To add login security:

• Go to Employees > Employees.
• Set a PIN Code for POS login in the “HR Settings”.

In the end, the only working solution was to manually remove the problematic element directly from the file .../navbar.xml.

This menu option is no longer available in the interface, and no users have reported missing it — so it seems safe to remove.

Also, please note:

This “issue” appeared specifically when using Windows 7 Server in combination with the Firefox browser.

After switching to a more up-to-date system (Ubuntu/Pop!_OS with Chrome browser), the problematic menu item is no longer shown to employees.

To restrict waiters from installing apps and printing reports in Odoo POS/Restaurant, you need to adjust the user permissions. Set the 'Access Rights' for the waiter role to only include necessary POS rights, and ensure they don’t have access to 'Settings' or 'Reports' under their group permissions. You can do this by creating a custom user group with limited access or modifying existing groups.