Now, on a map only symbol markers like museums etc. and markers with auto-counted numbers are shown. At Wikivoyage/de we need also user-set numbers and texts written on the markers. This is mainly for backward compatibility.
GeoJSON properties must be extended by an additional marker-symbol attribute like "-user" and a new property like "marker-text". User-set numbers and letters must be analyzed to prevent these values from auto-counters.
This task was mentioned at Community-Wishlist-Survey-2017 (https://meta.wikimedia.org/wiki/2017_Community_Wishlist_Survey/Miscellaneous/Kartographer_improvements), which got the No.1 out of 214 proposals.