Join sub-catchment centroid using line and import attributes of it using QGIS Model builder

Question

Input Data: I have a sub catchment polygon shapefile, which contain following details

Name	Description
TG_ID	Name of the Sub-catchment
Hoehe	Average height
Slope	Average slope
UTM_x_m	centroid x value
UTM_y_m	centroid y value
Km2	Area

The link to the input data: enter link description here

Workflow that I wish to accomplish:

1. Create centroid point shapefile of the sub-catchment (vector-->Geometry-->centroid, which take the properties of the polygon shapefile automatically)

2. Create a line shapefile and connect the centroid of the sub-catchments - manually (How sub-catchments are connected to each other)

3. Now I am expected to create an “TG_TO” attribute in this centroid shapefile layer, how these sub-catchments are connected to each other. For example, like below

Is there any way to automate this in QGIS model builder ?