Feature request #9001
Make imported CSV tables editable within QGIS
|Pull Request or Patch supplied:||No||Resolution:|
I think this would really improve the usability of QGIS and is probably not that hard to implement (i would guess). Just needs a connector and table-writer for QGIS to change cells and write new rows to an existing file.
See this and many other GIS-SE question where someone wondered why they can not edit a loaded table.