Append one layer to another in QGIS

I am a long time user of various GIS packages and am starting to explore QGIS in more detail. I have a polyline shapefile with some multipart features. I did not create the shapefile, but must edit it to fix the multipart features – they need to exist as single part features. Its easy enough to run the Topology Checker and create a "must not have multi-part geometries" rule to identify the problematic features. Its also easy enough to select the offending features and run the "Multipart to singleparts" tool to get single part features.

I noticed that the default output is set to [Create temporary layer]. Is there a way to set the output as the original layer instead of creating a temporary layer? If not, then what is the "normal" process for appending the layer containing the single parts into the original layer that had the multipart features? Naturally before I would append the temporary layer, I would delete the multipart feature from the original layer.