Good question. If the job is created outside of the asset bundle, and exists before this bundle will be used for the first time you can use a lookup variable
variables:
your_job_id:
lookup:
job: "your_job_name"
If it's created inside the same bundle you can reference it directly
${resources.jobs.<job-name>.id}
I've not tried these in anger though, so let me know how you get on.
https://docs.databricks.com/en/dev-tools/bundles/variables.html