That is not currently possible (because you can’t create a FileList); however I think I can workaround this limitation. It’d be great if you filed a feature request in the Inputs repo.
My work around was to have one cell with :
teFile = file || FileAttachment("nz-8m-digital-elevation-model-2012@2.tif")
And another with :
Tiff = await teFile.arrayBuffer()