You need to set up outbound documents for dunning so the created dunning letters will be listed under “Outbound Documents” in the menu where you can then continue to process them either one by one or collectively.
Follow these instructions and pick the Table Dunning type and the Print Format Mahnbrief (swat).
Note: Should the print format not be available, then add a new one and use the Table
C_Dunning_Header_v
and the Jasper Process Mahnbrief (Jasper).