Ironically I worked on adding adding taxes tonight and checked here earlier to see if you had a chance to respond yet. Thanks.
So what I ended up doing was just creating a new .csv manually from the taxrates.com and uploading it. For Oklahoma there are 764 entries and sure enough it slows down the page to a crawl without your plugin activated.
What was a major time saver was using your plugin to remove all entries so I could re-upload an edited .csv through woocommerce. Major thanks there to you.
I hunted through your code but I couldn't figure out where you addressed priority. I figured you left it blank and it just defaulted to 0.
What would you like the priority set to? By default I have it set them all to 0... not sure why you would want it anything else. Your importing hundreds if not thoasands of zip codes so why would the priority be in any other order or why would one have priority over the other it would be irrelevant.
Here's what I encountered. If priority is set to 0, you can not add another line with a 0 priority. It has to be 1 and up. Woo won't let you. All of the priority 0 entries are highlighted in red as an error. They cannot be adjusted either.
So any additional line you wish to add (say for instance for a pay locally option which calls the home state line) is forced to have a priority of one by woocommerce restraints.
Anyhow, it just occured to me that I could add my additions into the taxrate.com .csv in excel before using your plugin to upload. That would work as well and take less time than I spent today making a new excel template.
Hey thanks for your plugin.