Until now I was saving styles in QML files. Now I need them in SLD to be used in GeoServer. Is there a way how to perform a batch convert?
AFAIK In this moment (qgis 3.6) you can't without writing some simple python code.... but I could be wrong. May I suggest to do a feature request in QGIS (better offering work to a core dev or hoping someone will dev for you)? adding a processing algorithm doing sld export is simple and than use it in batch.