Whether this registration is hosted by a section rather than by a slot.
A contribution that names fields renders at the top of the section drawing them, which
<mj-form-field-panel-slot> mounts. It still carries a slot, because every row does,
so a slot host that went by slot alone would mount it a second time at the bottom of the
form — the same panel twice, once in the group and once as a section of its own.
Whether this registration is hosted by a section rather than by a slot.
A contribution that names fields renders at the top of the section drawing them, which
<mj-form-field-panel-slot>mounts. It still carries aslot, because every row does, so a slot host that went by slot alone would mount it a second time at the bottom of the form — the same panel twice, once in the group and once as a section of its own.