Thank You for reading my article Bjarne! :)

If you open the Job Cluster & navigate to its "Libraries" tab, you should be able to select the custom library for the cluster to install it on start-up.

If the library is installed on cluster startup, I think it should be available for all tasks, given that those tasks are executed by this cluster.

If you have many clusters, all running tasks, but you need to install a given package (custom or regular) on all of them, you can create a Global Init Script (Settings -> Admin Console - Global Init Scripts tab) that runs on each cluster on start-up. The only thing to be careful about with this approach is, if you have clusters running different versions of Databricks Runtime, the Global Init Script must account for this, otherwise the cluster start-up can fail.

Best Regards,

Tibor Vékony