On Courseplay there is also button "Calculate current field's edge path" (or something like that) which will register modified/merged fields true edges. After calculating fields edge path you can save the new edge path and use that for generating courses.

About 950, trying to reach 1000 hours before FS22 release

Not sure if we are allowed to post links for 3rd party mod sites but I can tell you that the seeder you are looking for is Great Plains 3S-3000HD. You can find it yourself with google.

New mods are out! Ellerbach got updated for Manure System.

I usually open GlobalCompany UI (default Lctrl+G) while I'm not standing next to potato sorter but further away and spawn pigfood using that UI.

Try Ellerbach. It has small fields, roads and yards.

That setup is correct for harvesters also. Only change is of course right hands left/right being rotating of the harvester head. Left for counterclockwise rotation and right for clockwise.