While using ArcGIS you know that using special characters in field names should cause problems. The same problems will happen while using data with special characters in field names in atlasFX as atlas vector layer. In atlasFX special characters could cause problems while loading, displaying and querying the data. The special characters ä, ö, ü, Ä, Ö, Ü, ß are allowed but it is recommended to avoid them already during the data preparation in field names.