Transform multiple files in multiple folders and create that folders at the same time.

My prefered method is by building the output file path as an attribute. You can expose an fme attribute called 'fme_dataset'. This will contain the full path to the input file. You can use a StringReplacer to replace the input path to the output path

So if your input files were:

C:\\topfolderinputpath\\input1\\files.ext

C:\\topfolderinputpath\\input2\\files.ext

C:\\topfolderinputpath\\input3\\files.ext

C:\\topfolderinputpath\\input4\\files.ext

You could replace "C:\\topfolderinputpath" with "C:\\topfolderouputpath", you would then have:

C:\\topfolderoutputpath\\input1\\files.ext

C:\\topfolderoutputpath\\input2\\files.ext

C:\\topfolderoutputpath\\input3\\files.ext

C:\\topfolderoutputpath\\input4\\files.ext

This attribute can then be used in a FeatureWriter as the output file location.

The alternative is to use the fanout option in a normal writer. It doesn't preserve the input structure and you again need some way to build the folder structure as attributes

Here is some info on using fanouts: https://community.safe.com/s/article/fanout-1#:~:text=A%20fanout%20is%20a%20way,type%20fanout%20and%20dataset%20fanout.