“Hi everyone! I’m trying to change my checkout’s ‘Postal code’ label to מיקוד (חובה). I have already updated all the fields in the ‘Edit default theme content’ section, but the changes are not showing up on my live checkout page. I am using the [Insert Your Theme Name] theme. Could someone please share the custom code I need to make this change stick? Thank you!”
That’s a proper way to achieve what you want.
However, it may be difficult to find “the one” translation as some may look similar, so just keep trying.
And make sure you’re editing proper language – the same one you see at checkout.
No custom code can be applied at checkout (in most cases).
Hi 
Checkout labels aren’t controlled by the theme. If you’re on Shopify Plus, you can change them using checkout customization.
If you’re not on Plus the checkout is locked so edits in Edit default theme content won’t show on the live checkout The label will only change if the store language supports it.
Hope that helps!