Building Jenkins pipeline with GitLab info I am new to DevOps world and desperately looking for your help.
We have multiple API depositors in GitLab subgroup, I am trying to establish a CI/CD pipeline, which will connect to GitLab subgroup,

Any new API added into the subgroup, the pipeline will be triggered.
If existing API code is updated into any branch pipeline should be triggered.

In GIT repository, I have to provide the API URL, should I write #of pipelines as number API?
Gitlab Subgroups are essentially only additional path identifiers on the Gitlab server.

For example if you have:  


Gitlab server on localhost   
Group: test
Subgroup subgroup1  
Repository myawesomerepo


Then the path to your repository will be:

http://localhost/test/subgroup1/myawesomerepo


And cloning the repo will be

git clone git@localhost/test/subgroup1/myawesomerepo.git


So when you connect any Jenkins pipelines to the repo you will need to connect them to that full path.  

Any changes being done or API's added to the Git repository itself can easily be monitored automatically to do some action via Jenkins.  

However, since a Gitlab Subgroup is not a Git feature rather a Gitlab feature, you need to try and write you own logic to query on the full URL and to see if there were any new Subgroups/ API endpoints added.