Hi,
thanks for help.
I was surprised myself it worked so far, but tried because the masterfields where selectable as an option.
The scenario is like this:
Provincial administrative units having: provinces, districts, subdistricts
Local governmental units having: cities, city districts, city subdisricts
Cities can be allocated to one or more of the provincial units (bounderies overlapping)
Roads segmented with links to: junctions, crossings, buildings, traffic, behavior, ...
Can be allocated to local units
Directory: business branches
Can be allocated to road segments
Other city elements: public places, buildings, landmarks, ...
Most can be allocated to road segments
For the city/road part I created two content types "road" and "road segments". At road content type item I do the assignment to the governmental and local bounderies. At road segment content type item I defined 3 field groups: road start (single value), road middle (multi value), road end (single value). In the multi value field group I assign roads, junctions, crossings, branches, etc. All the field groups have selectable districts/subdistricts in common, refering to a master field "city" out of the groups because same for all road segments. A road can pass different bounderies so districts/subdistricts can change each segment. The "city" master field outside the group would prevent typos doing the same choice on every multi fieldgroup. Without the city reference I get thousands of option values to select.
Is there is another way without coding to get the value of a custom field outside a field group (for example useage in a sql query at FE/BE edit mode)?