If what you have is manual trunk door, then no release button, anywhere in keyfob nor beside seat button.
The open trunk door from factory only works for power back door (with motor inside). Because thr manual one doesn't push open wide when unlocked, it still requires human intervention to push open the trunk door. So, no button.
Can you install aftermarket power back door, new keyfob button and open trunk in interior? Yes, there is aftermarket installation one