You can actually list all pipelines triggered by schedule using GitLab REST API
GET /projects/:id/pipeline_schedules/:pipeline_schedule_id/pipelines
Your request attributes must contain the project id and the pipeline_schedule_id as both are required. You could replace the project id with the URL-encoded path of your owned projects.
Example Request:
curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/projects/29/pipeline_schedules/13/pipelines"
Example Response:
[
{
"id": 47,
"iid": 12,
"project_id": 29,
"status": "pending",
"source": "scheduled",
"ref": "new-pipeline",
"sha": "a91957a858320c0e17f3a0eca7cfacbff50ea29a",
"web_url": "https://example.com/foo/bar/pipelines/47",
"created_at": "2016-08-11T11:28:34.085Z",
"updated_at": "2016-08-11T11:32:35.169Z"
},
{
"id": 48,
"iid": 13,
"project_id": 29,
"status": "pending",
"source": "scheduled",
"ref": "new-pipeline",
"sha": "eb94b618fb5865b26e80fdd8ae531b7a63ad851a",
"web_url": "https://example.com/foo/bar/pipelines/48",
"created_at": "2016-08-12T10:06:04.561Z",
"updated_at": "2016-08-12T10:09:56.223Z"
}
]
Reference link https://docs.gitlab.com/ee/api/pipeline_schedules.html#get-all-pipelines-triggered-by-a-pipeline-schedule