[galaxy-dev] How to modify "save" icon

Hello, The tool "SAM to BAM" generates a dataset from which it is possible to download two files (instead of one) from the icon "save". As my script generates an output result and another txt output containing information about linux command, I will wish not to generate two datasets in history but only one dataset with two files downloaded from the icon "save". Do you know how to encode the corresponding xml? Moreover, I would like to add file formats of file which can be opened in the central window central of Galaxy (thanks to "eye" icon). Do you know, please, how to add more files formats ? Thanks in advance, Sarah Mom