Hi, There seems to be a weird bug with the "Input dataset" workflow control feature, hard to explain clearly but I'll try my best. If you define a custom datatype that is a simple subclass of an existing galaxy datatype, e.g.: <datatype extension="myext" type="galaxy.datatypes.data:Text" subclass="True" display_in_upload="true"/> And if this datatype will be the input to a workflow where you want to use the multiple input files feature you must put into your workflow editor an "Input dataset" box at the beginning and connect it. If you define a custom datatype that's it's own custom class, e.g.: <datatype extension="myext" type="galaxy.datatypes.data:MyExt" display_in_upload="true"/> with a simple class in lib/galaxy/datatypes/data.py e.g.: class MyExt( Data ): file_ext = "myext" And if this datatype will be the input data to a workflow if you have an "Input dataset" box at the beginning for some reason the drop-down menu (or multi-select) won't not have files of this type from your history it just ignores them. Now what is strange is if I edit the workflow and remove the beginning "Input dataset" box and start the workflow with just the first tool which has this custom datatype as an input parameter then when I try to run the workflow everything shows up properly :-/ Hope I explained this ok, seems like something is broken with the "Input dataset" workflow control feature. best, Leandro