Help with Blueprint Send TTS Notifications to multiple mobile devices

I have the following: action in my blueprint:

variables:
  iDevs: !input notify_device
...
sequence:
  - alias: All Devs
    repeat:
      for_each: "{{ iDevs }}"
      sequence:
        - action: notify.mobile_app_sm_s918u
          data:
            title: "{{ title }}"
            message: "{{ message }}"
            data: 
              tts_text: "{{iPrefix}}{{data.tts_text}}"

I would like to determine the action based on the templated name repeat.item instead of the hardcoded “notify.mobile_app_sm_s918u”

It isn’t always possible to directly correlate a device name or entity ID to the to its notify action. If you maintain strict naming/ID-ing conventions you can use something like what is shown here. You have not provided enough information about what is contained in iDevs for a more specific answer.