Any otbcli can make use of band selection, eg.
otbcli_ExtractROI -in QB_1_ortho.tif?bands=1,2 -out example2.tif
is there an equivalent trick within the QGIS Processing Toolbox?
Indeed, one can’t use the extended filenames through the QGIS interface. It would be an interesting feature. And I don’t know of a trick…