Custom UI for the FlowAApps.

FME Flow Apps support:

• Custom logos
• Custom colours
• Custom banners
• Custom descriptions
• Gallery Apps for application navigation

This is the lowest effort option.

Instead of users seeing an FME Flow App: your next option is to go full custom

1. User
2. Custom Website - with all your CSS, HTML including javascript to call :
3. FME Flow REST API 

• POST /fmeapiv4/jobs   to execute the Workspace / Automation parsing in parameter
• GET /fmeapiv4/jobs/{id}/result to retrieve data download result URL

javascript example

const response = await fetch(
  "https://yourfmeflow/fmeapiv4/jobs",
  {
    method: "POST",
    headers: {
      "Authorization": "Bearer " + token,
      "Content-Type": "application/json"
    },
    body: JSON.stringify({
      repository: "GISTools",
      workspace: "ValidateMyData.fmw",
      publishedParameters: {
        INPUT_FILE: filePath
      }
    })
  }
);

const result = await response.json();
console.log(result);

Lastly, you can post an FME Idea for Safe software to develop a better custom UI generator for what you’re asking for here

​@madhusudan Add your thoughts and ideas to this: Improve Customize Options for FME Flow Apps | Community

Just as a side note, it’s incredible what you can accomplish over a few hours using something like Claude Code or Codex. If you feed it the FME Flow REST API definition as part of the specification, the sky’s the limit :-)