oh i don't know if you already know this -
you choose 8 subjects for the whole year so only 4 per semester (this is recommended because it pans out well for 3 years without overloading on any) and one of the 8 has to be a core such as 'power', 'identity', 'reason' etc etc which you can find the descriptions of in the handbook. to be honest, i think those stuff are absolute bullshit but anyway, it's compulsory for arts.
and also, the reason why there are many drop downs is because it doesn't only cover your first year but all three years. so far you have nothing to worry about and only have to enrol your first year (some people are even planning to enrol first semester only).
as for 'discipline subjects', they are just electives and because you plan on doing two majors, there wouldn't be enough space for you to do many so as long as you fit the 4 subjects per semester thing then you're fine.
sorry this has been all jumbled but this is what i've been told over the phone (spent about 40mins of international call credit haha) by a very helpful young lady. so i hope this helped!