They are not combined. For capturing LOC and G/S you use APR mode, there is APR button on AP panel between HDG and NAV.
NAV mode is used for FMS or VOR navigation.
But. for both modes - NAV and ILS(LOC) you need to choose your CDI source on Primary Flight Display (PFD) - using CDI soft key at the bottom. It's usually set to FMS - then you have magenta coloured HSI. This source if used for flight plan following. Pressing CDI softkey cycles between FMS, NAV1 and NAV2 sources. When you choose NAV1 - HSI arrows turn green and allows you to capture and follow VOR or ILS - depending on NAV frequency set.
So logic is similar to boeing. You continue most of your flight in NAV mode with FMS source (magenta HSI) following your flight plan (like LNAV i Boeing). Then you change to HDG mode (for vectors for ex.), then you set your NAV1 freq for VOR or ILS, whatever you need, change your source to NAV1 (green HSI), and switch to NAV mode for VOR following or to APR mode for capturing LOC and G/S.
I'm not sure I made it clear. Feel free to ask, if not.