Create new nodes - testing not locally?

Greeting node-reds,

I am playing around with node-red on heroku for some poc projects with Salesforce Marketing Cloud.
Now I want to have some more reusable tools there and thought about to create nodes to speed up things and let my colleges participate.

I might be blind, but I cannot find how to deploy new nodes in my palette on my heroku instance of node-red. The documentation refers on "you can test it locally" but I don't have any node-red installed locally nor do I want to.

Is this a dead end for me?

Thank you