If they are not available in Studio, you can download Studio pro and use workflows, see below link
But if you just want to know when workflows would be made available in Studio, I’d suggest to contact Mendix support.
Hope this helps!
I’ve used Studio pro where you can use workflows.
But the learning path’s documentation is not aligned with the latest version and it is hard to finish the learning path.
I also wait for the updates to finish learning path for workflow.