Join attributes of outlets to subcatchment polygons in QGIS

The points to catchments plugin doesn't add the original attributes of the outlets. In this video we'll join the attributes of the outlets to the derived polygons of the subcatchments.
The vectorisation of subcatchments results in geometric errors. To solve that, we first dissolve the polygons in batch. Next, we merge all polygons into one vector layer so we can easily snap the outlets to the polygon boundaries. That is needed, because the outlets are in the centroid of the original DEM. In the next step, we join the attributes by location, using the "touches" parameter. Finally we split the subcatchment polygons in separate layers.

0:00 Introduction to the challenges
1:20 Dissolve subcatchment polygons in batch
2:50 Merge dissolved subcatchment polygons
4:14 Snap outlets to the subcatchment boundaries
5:18 Join attributes by location with the "touches" parameter
6:28 Check results of the join
7:40 Split subcatchment polygons into separate layers
8:55 Check the final result

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[truongannguyen]

Could you make a tutorial how to automate these processes? Maybe with the "Graphical modeler" in QGIS 3