There appears to only be documentation for modifying connection names via the console. Checking CloudTrail after modifying a connection name I see an event for ModifyConnectionName - the documentation and SDKs should be updated to include this action.
{
"eventVersion": "1.05",
"userIdentity": {
REDACTED
},
"eventTime": "2020-02-15T17:53:19Z",
"eventSource": "directconnect.amazonaws.com",
"eventName": "ModifyConnectionName",
"awsRegion": "us-west-1",
"sourceIPAddress": "REDACTED",
"userAgent": "aws-internal/3 aws-sdk-java/1.11.706 Linux/4.9.184-0.1.ac.235.83.329.metal1.x86_64 OpenJDK_64-Bit_Server_VM/25.242-b08 java/1.8.0_242 vendor/Oracle_Corporation",
"requestParameters": {
"connectionId": "REDACTED",
"connectionName": "REDACTED"
},
"responseElements": {
REDACTED
},
"requestID": "70c2da3d-50cd-4778-8ef5-fb96d64153de",
"eventID": "750fca32-eb81-4966-a293-5a834605181c",
"eventType": "AwsApiCall",
"recipientAccountId": "REDACTED"
}