[quoteîIn the Calendar menu, the GUI shows all 365 days, and allows us to just toggle the status of each day, between working holiday.
So, for example, if I have to change a weekend from Sat+Sun to Fri+Sat (as in the Gulf), I have to click the calendar 104 times!
There should be an easy way to define the weekly off easily (say a list of all weekdays with a checkbox against each).

this already exists on global parameters.then calendar defines exceptions.

The GUI also does not allow us to enter holidays with a note attached (to remind us what the holiday is for).

just because calendars are not desugned to enter holidays. Forget about ms-project way to do. Have a look at administrative projects...

Thirdly, the GUI does not capture other attributes, such as working timings (with preferably a definition of a lunch time as well).
It should also record if the office timings are different on specific days (for example, on Saturdays, some offices open earlier, and work for only half a day.)

such feature is not planned as projeqtor does 'ot manage time. It plans some work for earch day but won' t tell when it the day it is done.