LLM / AI / OpenAI workflow with file input

Hello .

I want to create a workflow with existing nodes and without any Java/Python-workarounds to ask a local LLM. Everything easy, as long as the input is text only. But I need to have the input both: A file (binary) and a text with the prompt. As far as I can see, there are no nodes fitting this purpose out of the box.

Did someone already made this? Is there a methodology where you can e.g. create something like a “multipart-form”, meaning you kind of join the file and the string to a mixed data stream (e.g. a JSON) and send this to the LLM?

Thanks for your thoughts and solutions on this already upfront.