I have two questions related to the request attributes.
First, is it possible to change/rename Request Attribute ID? We'd like to use IDs generated using our own logic.
If changing the request attribute ID is not possible, is it possible to create new with the specific ID? If so, should the ID be part of the JSON payload or in the request parameters?
So for Request attributes yes you can rename/change them. This can be done via the Settings>Server-side Service Monitoring>Request attributes.
As you can see in the screen shot, there are multiple variables you can configure to mask data, prune white space and or parse out data.
If you want to change the name of request this can be done in the same location but selecting Settings>Server-side Service Monitoring>Request Naming
It is not possible to change the ID of a request attribute, but you can create a new request attribute with a custom ID by using the PUT method in the API and providing the ID in the URL.