Working on QGIS 3.4.13.
I have a vector line layer, there are rivers. I put a rule based symbology with two categories and different scale max / min for each category.
I want to put style for the name of each type of river. I configured my legend in vector layer properties (following those steps : https://docs.qgis.org/3.4/en/docs/user_manual/working_with_vector/vector_properties.html?highlight=l%C3%A9gende#legend-properties)
I also checked this : QGIS styling a legend
So at this point I have this in QGIS
and that in QGIS composer
I also checked in QGIS 3.10.1, to see if there some more functions, apparently,no.