How to use a template for lock.enabled?

[Mattat01]

Can anyone help me understand why this does not work?

- type: custom:button-card icon: mdi:calendar-alert-outline show_icon: false name: Create Event lock: enabled: > [[[ if (input_text.event_title.state == "") return "true"; else return "false"; ]]]
Strangely, when I save it the "enabled: >" becomes "enabled: |"
The Create Event button does not even show up unless I put the [[[...]]] in quotes (which doesn't make it work either)

I've also tried:
lock: enabled: "[[[ return input_text.event_title.state === ''; ]]]"
(that is === then 2 single quotes) ,and a variety of slightly different versions...

The Create Event button does not even show up unless I put the [[[...]]] in quotes (which doesn't make it work either)

Basically, I want the lock to be on until the event title is not blank.

Thanks,
Matthew

EDIT:
Oh, I got it (Ok, Gemini got it). The below worked:
- type: custom:button-card name: Create Event lock: enabled: | [[[ return states['input_text.event_title'].state === ''; ]]]
I don't know why the > becomes a |, but it works like that. I also thought I'd tried every combination, including this, but there you go...