Thanks for reaching out! There isn't a direct way to convert your feature table to .xlsx/.csv within QIIME 2, but @Parikrama_Sapkota's suggested post does describe our best recommendation for going about this. In particular, I'd check out this comment - once you have your BIOM file, you can use the biom convert command (outside of QIIME 2) to convert that file into .csv format.