dual barcoding support

Welcome @liucong2021 !

Yes, dual-barcode demultiplexing has been supported in QIIME 2 for over two years now, see the 2019.4 release notes here:

This is only for unique dual-barcode pairs, not "combinatorial" barcodes (i.e., when the same barcodes are re-used for multiple samples; search the forum archives for more discussion about this and workarounds).

Good luck!