This seems to be a bug. I can't hide group and main_url columns. If I use
hideColumns=label,group,main_url it will hide label, but group and main_url remain.
I tried different combinations, group alone, main_url alone, etc. The result is always the same, group and main_url are not hidden.
It's actually kind of expected behaviour for the current implementation.
main_url are no real columns, but metadata. using
&hideColumns=label&disable_queued_filters=1 would hide them, as it disables the metadata processor.
Nevertheless it might be expected behaviour that
hideColumns would also hide metadata. ping @mattab
AFAIK it shouldn't. It would need a new parameter
hideMetadata or something maybe.