How do I use companion app for iOS actions/notifications?

I have some very basic questions about how iOS actions and notifications work, I just can’t seem to understand fully how it works. I am trying now take more advantage of the HA companion app on my iPhone 16 Pro and send different types notifications, and maybe run some actions… I can’t seem to do what I want to do because I don’t know where to start exactly.

A little background: I’m fairly new HA and don’t have too much coding/YAML experience… currently, I know just enough to scrape by with my own HA set-up, and that’s about it…
In terms of my current set-up: I’m running HA with HA Green. Everything is up to date with latest versions, including on the iPhone as well. I do not have HA cloud service set up though – just Firebase cloud messaging & local push option enabled in the app (and set to ‘Most Secure’ connections security level). I have all options on my iPhone (and the app) set up to have full access to my phone, including all sensors enabled/sent and permissions for location (always/exact), as well as allowing all notifications.

That all said, I can successfully send notifications to my phone through Automations using the “Send a Notification via mobile_…” action but that’s about it; I would like to do more, like send critical notifications, clear/replace notifications, etc. How do I do this?

I’ve read (and re-read) the official HA Companion app docs, along with Notification and Actions docs for HA, and I’m still not sure where to start and how I actually make it happen. I understand the basics of sending a notification and formatting message/title/tags, but am I suppose to code in all these basic commands/actions in the configuration file first-- like through the File editor? or do this all in YAML within automations? Or both?

Also, do I need additional integrations (for iOS or for Notifications in general) to make this happen?

I don’t mean to sound short-sighted or ignorant when I say this, but I would have assumed that if all these actions are possible (which they are – as described in the HA Companion app docs), then they would be available as actions within automations (in visual editor)… That doesn’t appear to be the case though, but please correct me if I’m wrong.

Judging by the fact I couldn’t find anybody else asking about this online (including on here), I am very aware this may just be ‘user’ issue lol, but any help would be greatly appreciated!