The rail item a contribution belongs to by virtue of the slot it mounts at.
A slot says where a panel sits in the form body, and the rail groups that body — so the
slot decides the group unless something more specific does. before-fields and
after-fields are positions among the field sections, and the field sections are the
Details tab, so a panel at either belongs in Details. The rest are positions relative
to things that are tabs in their own right, so a panel there is its own tab too.
Without this the slot has no visible effect on a rail form at all: every contribution
that claims nothing becomes its own tab, and a user who asked for "before the fields"
gets a tab at the bottom of the rail instead.
The rail item a contribution belongs to by virtue of the slot it mounts at.
A slot says where a panel sits in the form body, and the rail groups that body — so the slot decides the group unless something more specific does.
before-fieldsandafter-fieldsare positions among the field sections, and the field sections are the Details tab, so a panel at either belongs in Details. The rest are positions relative to things that are tabs in their own right, so a panel there is its own tab too.Without this the slot has no visible effect on a rail form at all: every contribution that claims nothing becomes its own tab, and a user who asked for "before the fields" gets a tab at the bottom of the rail instead.