Bingo !!!!! now it works. Thanks a lot Dannon.
To sumarize:
in the New output name window of a particulaenter: prefix #{input_file} or prefix #{input} depending on the tool being used
If you have several successive tools in your workflow be sure to do that for each tool if you want to keep track of the name of your input dataset. You end up with something like this in my case after 8 tools (each new prefix is in italic) but at least you keep the info that it concerns the IonXpress 018_TOR-126 dataset
118: IonXpress_018_TOR-126.fastq
213: Groomer IonXpress_018_TOR-126.fastq
214: FASTQ to Tabular Groomer IonXpress_018_TOR-126.fastq
215: Sort FASTQ to Tabular Groomer IonXpress_018_TOR-126.fastq
216: Tabular to FASTQ Sort FASTQ to Tabular Groomer IonXpress_018_TOR-126.fastq
217: Groomer Tabular to FASTQ Sort FASTQ to Tabular Groomer IonXpress_018_TOR-126.fastq
218: Filter Groomer Tabular to FASTQ Sort FASTQ to Tabular Groomer IonXpress_018_TOR-126.fastq
219: FASTA Filter Groomer Tabular to FASTQ Sort FASTQ to Tabular Groomer IonXpress_018_TOR-126.fastq
220: 500K FASTA Filter Groomer Tabular to FASTQ Sort FASTQ to Tabular Groomer IonXpress_018_TOR-126.fastq