multi-calls documentation/examples what's possible and what isn't

2 things I'd love to see. First of all I stumbled across that multi-call: by accident. Wasn't aware that's possible. You'll find if ever 2-3 threads about it in the ha community forum. Must be a well hidden secret. So may I ask for some examples for the lovely card? I know it's one of the sub-aspects the card offers in general since so not being disgussed a lot, but the potential is massive after I played with it, since it reduces the need for scripts or automations by some amount if being able to simply stick the code into the card itself. Though I never tried to figure out if a script or automation or a card containg multiple servicecalls being differnt in processing.

second one is one where I completely lost that the moment. As said I stumbled across a code snipped going like this:

  action: nothing
  multi-calls: |
    [[[````
with multiple hass.callService entry being js code.
What I do wonder if it must be js code or if I could use normal YAML aswell. Tried to adopt a snipped from an automation which did contain some - if: then: else: lines aswell as -cinditions: but I'm lost since no errors shown means no way to know what actually fails.

If not being possible and js is the only way, I got stuck in firing a hass.callService for mqtt.publish
Likely a syntax problem since I'm completely unsure about how to struct this call with topic and payload.
Within yaml my mqtt.publish looks like this:

service: mqtt.publish data: topic: enoceanmqtt/soft_4way/req payload: '{"R1":0,"EB":0,"R2":0,"SA":0,"T21":true,"NU":false,"send":"clear"}' qos: 0 retain: false
```
perhaps someone with an idea on how to solve that?
```

custom-cards / button-card

multi-calls documentation/examples what's possible and what isn't #659