- Remove subordinate, superordinate

NOTE: that switching between hierarchical and flat view will mess up the vue internel v-for:key ids and somehow result in wrong highlighting groups (same hovering element around different value?). A better key (JSON.stringify(fieldValue)) works but is not efficient...

Disable highlighting for elements that only have an ID but no other elements referring with idrefs to them

Fix style changes for list markers (id hover effects), @AK do not highlight definition children, reformat

TODO: check might be required for other field types as well?

TODO: needs check if there are at least idrefs for an id (or other ids), otherwise skip too