@RabbitZzZ, @toplakd, @datakick
As I get mad almost once a week about the misssing "update shipping cost", I decided to tackle this myself. I couldn't wait any multiple years longer for this feature. In my opinion it's over due... As we pointed out above, there is no super clean solution to this problem, but I believe that my solution now is quite acceptable. At least it's much a cleaner way than the free PS module uses.
Technically a new cart is created based on the order values. The cart is used then to recalculate the shipping cost.
I practice you can select the shipping method in an order and click on "recalculate shipping cost". This is very useful in case you have edited the order before. The select also allows to change the shipping method at all. This way you can change, in case your customer wishes so or you can also select a shipping method, that is only visible in the BO.
I haven't imlemented a amount input yet, but that would be possible too. I hope, that some expierenced user test my snipped (in a test store) and give a feedback. It's really hard to forseen every case. In my (quite simple) cases, the code seems to work properly.
https://github.com/eschiendorfer/thirtybees/commit/4ccd64465ff1e4b956e1caba1feb411b6ee834a3