Just like all other Garmin GPS devices, Garmin-Asus A10 GPS smartphone also supports multiple map and multiple custom POI file.
You can add maps into this phone by creating a new "Map" folder either in /storage or /sdcard and put the Garmin map with .img extension inside that folder.
Putting the file in /storage will utilize part of the phone's 4GB internal storage, and putting the file in /sdcard will utilize the storage in your micro SD card in the phone.
If the map comes with JCV file, create a "Garmin" folder either in /storage or /sdcard, and then create a "JCV" folder inside your "Garmin" folder, then put the JCV file inside it.
To put the custom Point Of Interest (POI) files into the phone, create a "POI" folder inside your "Garmin" folder and put the custom POI files with .gpi extension inside that folder.
Besides, the maps that preinstalled in the phone are resided in the /storage/.System folder.
When you have multiple maps in the phone, you might want to choose which map to use for your GPS navigation. Here is the place to do the selection: go to Settings > Navigation.
Then tap on the phone's Menu key again to show this pull-up menu.
Select "Map Info" and you will finally reach the place to select/deselect your maps.