Bind is to "Bind a network to a template."
Split is to "Split a combined network into individual networks for each type of device" Both use POST Source:
https://developer.cisco.com/meraki/api/#!split-network
https://developer.cisco.com/meraki/api/#!bind-network

Cisco Catalyst SD-WAN vManage Certificate Management APIs provide the ability to generate a Certificate Signing Request (CSR). This is a common operation when onboarding or renewing device certificates in the SD-WAN fabric. The signing itself is handled by a Certificate Authority, not vManage.

REST APIs follow a client-server architecture, where the client makes requests and the server provides responses. This separation of concerns enhances scalability and flexibility. REST is stateless, not stateful, and is application-layer (not Layer 2) and device-agnostic.

If you want to replace only a specific item for a particular item, then use PATCH.
https://medium.com/@9cv9official/what-are-get-post-put-patch-delete-a-walkthrough-with- javascripts-fetch-api-17be31755d28