Problem: Is it possible to use custom event properties (triggering a canvas) inside the canvas, e.g. for decision splits?
Example: Fire a custom event A into braze, containing a custom attribute "status = {X, Y}". Create an action-based campaign w/ trigger action "Perform Custom Event A". Inside the canvas, add a decision split step that separates incoming user into Path 1 (status == X) and Path 2 (status == Y), with "status" being the custom attribute from above.
Looking at the Braze UI and documentation this seems not to be possible. However, for message content customisation using liquid these custom attributes seem to be available: {{canvas_entry_properties.${product_name}}}
It isn't possible to branch a Canvas based on entry event properties.
As you said, the best you can do is to use liquid to distinguish which event or property was used in the message step.