Answered Publishing a custom package

You can make a transport package for your extra with either PackMan or MyComponent. Packman is better for simple things that won't be modified often, but has some limitations (e.g., it won't do resources). MyComponent has a steeper learning curve but handles more objects, provides much more flexibility, and has some tools to help you do things like internationalize and update your extra.

There is also Repoman, migxElementsManager, and some other tools, but I haven't used any of them.

You can then submit the package at https://modx.com/extras/