Modeling a service waiting for a message event sent by a backend

Hello,
My question is very close to the question asked by Pierre Deville on the 04/16/2019: ‘Send a message event via REST API’ : how are you modeling a service waiting for a message event coming from a backend and not from an other process ?
My point is that if I use ‘Receive task’ or ‘Catch message’, those two steps require to specify the catch message from a drop-down list in General / General tab.
My understanding is that this drop-down list is populated with message declared in throw message steps. I am wrong ?
So how can I configure these steps to specify catch message type, or is there an other way to modeling this?

FYI: I am running Bonita BPM 7.5.4

Thanks in advance

You are right, the drop down list is populated with message sent by processes throw in the same diagram.

But this drop down list also behave as a simple text input. So you can type the message name you want.
You simply need to make sure that the name you try to catch in the diagram match the name of the message that will be sent thrown by the call to the REST API.

Thanks Antoine for this quick answer, I will be able to go forward