I had to spend hours on chat with support to find out that it is not possible to change the "ship from" address on Shopify shipping labels.
When I started my Shopify store, I did not have a PO box. Once business picked up, I did not want my home address to be listed as the "ship from" address on my shipping labels, so I got a PO box that has a physical street address, which is a different zip code from where I ship. I couldn't find anywhere to change the "ship from" address on my shipping labels, so I reached out to support.
I ship from my home address but needed the "ship from" address to be my PO box on my shipping labels.
After waiting about a week to hear back from support on my original question (which no one could answer, by the way), I got back on with chat support and waited until they found an answer to my question since everyone I had spoken to had promised to get back to me with an answer but didn't.
Shopify has no way to change the "ship from" address on shipping labels. This is a serious deficiency in the Shopify platform and needs to be addressed.
The ONLY way to get the "ship from" address to change is to add a location in Shopify settings and MOVE ALL YOUR INVENTORY TO THAT LOCATION. But you know what? There's NO WAY to move inventory between locations using the bulk inventory editor. You have to download all your inventory in a CSV file, change the inventory columns (remove quantity from one location and add to the other) and then re-upload this to Shopify and PRAY that you didn't make some sort of mistake because this process affects every entire item in your inventory: I have over 1000 items. Also, this doesn't address the issue of the label barcode being correct based on shipping from one zip code but having your return address be another zip code.
Let me be clear: I have been selling online for DECADES. I've used many online selling platforms and many online shipping platforms. Each and every platform has the option to set the "ship from" address on shipping labels. Shopify does not.
Shopify either needs to have the "ship from" address on shipping labels be unlinked from inventory locations (as an option) or needs a full-proof tool that allows you to move inventory from one location to another. Moving the inventory, however, does not address the issue of the barcode on the shipping label being correct.
All other shipping platforms can do this with no issue. Shopify needs to figure it out. I spent frustrating hours trying to get this fixed for my store to find out I cannot.