The zone and channel currently selected is known as Zone/Chan State, and the radio stores Zone/Chan State whenever it changes. By default, the radio will power up in the recorded last Zone/Chan State (i.e., the zone and channel that was selected at power down).
Offhand, I'm not aware of a parameter with APX that could be set to have the radio power up in Home Channel, versus powering up in the Zone/Chan State channel. However, there is a trick that works with the XTS family that may work in APX. (I haven't had an occasion to test it with APX yet.)
Usually, one programs an XTS to change Zone by programming one soft key for "Zone Up" and the adjacent on for "Zone Dn." And usually, the CPS rejects attempts to program the same function for more than one of a soft key, menu item or button or switch. However, if you program the A-B-C switch for "Zone," the CPS (and ROS) will permit this to co-exist with the ZoneUp and ZoneDn softkeys. So programmed, Position A puts the radio in Zone 1; Position B, Zone 2; and Position C, Zone 3. Moreover, regardless of the position of the A-B-C switch, you can then switch to a different zone using the softkeys.
However, on power up, the radio will revert to whichever zone is indicated by the position of the A-B-C switch.
One of my working radios has three working Zones, depending on my location. The first couple of channels are the same in all three zones, so looking at the display may not make clear what zone I'm in. However, I leave the A-B-C switch in Position A, and if I change to a different zone (using the soft keys) and then forget to put it back in Zone 1 when I power down, the radio will still power on in Zone 1.
This would not give you a power up Home Channel revert, but it would give you a power up "home zone" revert.
So far as I am aware, using the feature this way is undocumented in the Help files.
Here is a second trick that, while not exactly what you want, may be helpful. There is a feature (I can't recall the name from memory, and the programming computers are not handy at the moment) that enables the "1", "2" and "3" numeric keys to serve as "Radio Buttons" if no other feature is watching the keypad (i.e., you're not in "Page", "Call" or "Phone" mode). Once enabled, each of those keys works like the re-settable buttons we used to have in car radios (if you're old enough to remember). Select a zone and channel. Now a long press of one of the "Radio Buttons" will store that Zone/Chan State in memory, and, if the radio is selected elsewhere, a short press of the Radio Button will cause the radio to jump to that Zone and Channel.
In the radio mentioned above, we have a Dispatch Channel (F1) and two administrative talk around channels (FX and FY). If I want to talk to one of the people who have these channels without putting my traffic over the dispatch channel, I call him on F1, request change to FA, press numeric "2", and we conduct our business. At that point, a short press of numeric "1" gets me back to dispatch.
I have tested this feature on the APX and it works the same as with the XTS.
Caution: Using either the Home button, or one of the radio buttons, will cause the radio to jump to the stored zone and channel, regardless of the position of the rotary channel switch. However, if you then move the rotary switch, the radio will jump to the channel position now indicated by the position of the rotary. E.g.: I'm selected in Zone X, channel 6. Now I press "Home," and jump to Zone 1, Channel 1. Fine. But if I want now to shift to channel two and turn the rotary one notch up, I'll be on Zone 1, channel 7, not Zone 1, channel 2. If you enable the Home button with line troop radios (we do) or the radios buttons (we don't), this is a training issue, particularly if the troop radios are usually under cover and the troops usually use Command Mikes to change channels.