Assign Trucks to Forestry Tower

Allow assigning trucks to forestry towers, so vehicle management can be handled in 1 screen without having to hunt down individual tree harvesters.

why there already assigned to the tree cutter

tigerpanzer6666 Because if you have 10 tree cutters each with 5 trucks, you have to manually find each tree cutter to manage its attached trucks. It would be a lot easier if there was just one UI in the forestry tower to add or remove trucks.

This is done as you can leave your tree harvesters completely neutral, i.e. not assigned anywhere. They will then work wherever there is a tree ready to cut. If you assigned trucks to towers then they wouldn't be able to move around with the cutter. To keep the cutter 'portable' the truck needs to follow it.

On the one hand, I do agree that the current system gives rise to an issue where it's annoying to change the truck-to-harvester ratio for a lot of harvesters, or for one specific harvester if there's one that isn't right. This would probably only happen when changing forestry areas.
On the other hand, if trucks were managed from the tower like with mining towers, that would mean that there's a danger that, like with mining towers, trucks can sometimes go stupid and mob a small minority of harvesters, leaving others unsupported. And it would be much harder to observe the problem at a glance with tree harvesters under forest cover and widely scattered. So between those two options, I choose the current setup.
I think what would be ideal is for the forestry control tower's control panel to be able to differentiate between "tree harvesters with 2 trucks" "tree harvesters with 3 trucks" etc. for easy management. As it is now, we just have to be careful when reassigning harvesters.