There is an administration-API for creating UIs, reading audit logs, registering webhooks, etc.
The API can be consumed using Insomnia or Swagger.
One way to explore this API is to download the Insomnia workspace insomnia.json. Insomnia can be used either directly for all administration or just a way to explore how the API can be integrated in an existing interface/UI.
Under GII where is an environment selected (Test). Click Manage Environments and enter your id and password for Test.
Documentation about each request can be found under the requests docs-tab.
On way to access the API is to download the Swagger specification swagger.yaml. The swagger specification can be used to generate API code for different platforms, explore the API using e.g. Swagger UI or converted to e.g. RAML or other API specification languages.