I have a DEM which I like to update with a line feature to get some kind of line extrusion. Every cell of the dem overlapped by the line feature should have for example +10 added to it's raster value. Which tool could I use here in QGIS?
You can use r.carve within QGIS and set up a negative stream depth to increase the height of your DEM along your line feature
(In the image below a positive stream depth have been applied to the DTM)