Hi,
I think by default there is no print option. You might activated it from the settings after activating the developer mode, Settings -> Technical -> Reporting -> Reporting, search the report Leave Summary, then you might have clicked the Smart button with the label Add in the Print Menu .
The same report is printed from Leaves -> Reporting -> Leaves By Department .
The menu=False set in the code can be seen here: https://github.com/odoo/odoo/blob/12.0/addons/hr_holidays/report/hr_holidays_reports.xml
The code of the report is set such a way that it takes input from the wizard and print the data. So you are getting the above error message.
Thanks
Yes, I activated it from settings. Is there a way I can use that button to print individual leaves.