Do you want to show 1 size chart as a button and then another size chart as a separate button?
By default multiple size charts matching on the same product are grouped together. However, you can make specific size charts show separately by using the size chart's advanced injector setting.
In the size chart editor (**not settings!), click on the "advanced" tab. There is a special inject settings
Now toggle it, and then you can set up a separate injection selector only for this size chart. And then size chart will be injected independently.
Using this method, you could display more than 1 size chart buttons from Kiwi Sizing on your product page!