Link student registers to custom groups

It would be useful to have the option to link custom groups to student registers so that we only need to update any pupil changes in one place and can still contact everyone.

Alternative on the registers tab it would be useful to have a "or" option so that for example we have a pupil on two bus routes and currently by selecting both bus routes it will then filter out all other pupils as it is an "and" query function. By having similar options to the Query Builder in this section would make for much use.