Thanks for your help. However, unless I'm missing something, it seems that the methods described there output strings. For example:
... | fieldformat number = replace(replace(replace(number,"\.","#"),",","."),"#",",")
outputs the correct format, but it will be of string type. If I wrap the right-hand side in tonumber() it does not output anything (null), probably because it does not recognize the number format...
-- Edit --
The example above only works for replacing the . (dot) by a, (comma). I think because the default thousands separators (comma's) are added afterwards by splunk.
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