Hi @mike.b​, you can certainly upload multiple files at a time in an FME Server App. For the source dataset parameter, the user can select/drag and drop more than 1 file at a time. You should see the multiple file names appear in the form (i.e: File1.txt File2.txt). Browse Resources will open the file browser showing the temporary uploads and which files have been selected to be read into the workspace (shown on the right side). The space between the filenames tells the Reader to treat them as multiple files.

What file format is being read into this workspace? Do the files have different schemas? Could you please describe what type of translation you're doing with the files?

They are all flat files with the same schema (the source system can only extract a file for a given day). The workspace must then merge the files into one dataset for subsequent processing. - Thanks for your reply.

You'll want to use the Single Merged Feature Type for the reader as shown in the screenshot below. If you've already created the reader, simply open the General Parameters > Parameters > select Merge Feature Type.

All uploaded files will be read with this <All> reader and merge their features together. To test this out in FME Workbench, next to the file path parameter, open the dropdown menu and select "Multiple Files". I hope this is the solution you're looking for!