I don’t know if creating a custom sampler yielding multiple indices would work, as I would expect to see issues in the fetch method, e.g. here.
However, you might be able to use a BatchSampler as described in this post which would allow you to pass e.g. a list of indices to the Dataset.__getitem__ method. You might need to “encode” this list (e.g. first part is index0, second part is index1 etc.), but it could work.