As I understood, for example for someone who has a 1 month annual leave, we have to book leave for the normal working days and block out unavailability for the normal non-working days.

Since this has to be done in 2 different sections, it may be easier to have a page that shows the combined input (maybe in calendar form)?

Oh and to show the staff on leave on normal roster (eg faded out or in bottom row) will also be a nice plus...