Is it possible to add to a hydra defined elsewhere?

[AtomicNess123]

Let's suppose there is the hydra defined in a package, and I want to add a few actions to that hydra.
How should I add to that hydra?
Thanks!

[E3D3]

You can easily adds new heads to an existing hydra with defhydra+, for example:
(defhydra+ some-existing-hydra () ("x" new-command "new head"))
You can find a little more info about this in issues #185 FR: Function to add heads to an existing hydra and #381 defhydra+ is missing documentation.