Based on that circuit, turning off the ignition will de-energize the continuous duty solenoid and isolate the aux battery.

So you're asking if that circuit will allow you to self jump?

In that case, no... not if the main battery is completely dead. Why? The continuous duty solenoid will not energize because it is connected through to the rocker switch, the ignition switch, and then the main battery (which we assume is completely dead).

However, if the main battery is not completely dead, then yeah, the solenoid can energize and connect the aux battery to the main battery (in parallel).

I suggest the rocker connect to a relay sourcing power from by the ignition switch to automatically energize the solenoid. This would be the normal position. Then other side of the three-position switch sourcing power from the aux battery as the self-jump position. Center would be both circuits disconnected.