I believe I already explained this in an earlier post. As far as I am aware the only way to link banks is via the RT software. Scanning single banks is done by pressing F BAND, turning the encoder knob to select the band name and the pressing BAND again. Once the bank is selected press F SCAN (number 2) to begin scanning. If bank are linked, selecting a bank will scan all linked banks.
All of this assumes you have programmed banks and named them. Refer to RT software and FT70 manual.