Kestrel...I did a full diagnosis myself..compare my results..
1. BMW Factory Alarm = locks/open doors and trunk
2. Driver's Door (turn key all the way to the right)= double locks all door and trunk*, locks fuel door, closes all windows left open**
3. Passenger door = mines don't lock anything, only opens all doors and trunk.
4. Trunk* = (the trunk is the most interesting on the E36) with all doors locked turn key right it unlocks doors/trunk and fuel door. turn key left and it double locks doors and fuel door.
*okay, I haven't figured out this pattern-but you can do something with the key in either the drivers door or the trunk lid lock-where the trunk lock becomes completely independent from the door locks and the keyless remote. So the trunk remains unlock when closed, even if the keyless remote locks the doors. But once you double lock the door (or trunk) with the key then the trunk locks when everything else is single locked. Kestrel this may be your solution.
I think you turn the key on the trunk lid all the way right (or left) and hold it for a few seconds then the trunk unlocks and remains unlocked...to reverse this you just trun and hold the key in the other direction.
**hold key at far right position for 3 seconds...then keep holding and watch your windows go up.