How can I upload shipping rates using a CSV file?

Lately we are having to update and maintain this table more frequently as we are getting a barrage of pricing updates. Setting the table up in 250g increments up to 4Kg to make it somewhat manageable. But to add to the inability of uploading a csv file and being done with it, we have to also deal with the absolutely crazy way it stores /sorts entries. It seems you have to start at the high sizes first then go down else you get a crazy order like the following:

Storing the order correctly or being able to move them about would be useful.

A CSV file import would be a great improvement.

A formula to add based on weight would be perfection (per item + per Kg or g as most shipping couriers price in that manner) and a ceiling max which would make it add another parcel for products that can be split - ie add another per item charge after that threshold.

The current method is very error prone and the crazy ordering it’s doing makes it unmaintainable.