Move robotic arm with Moveit! without specifying end effector rotation

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Hello everybody. I face and issue which I think everybody who work with robotic arm should face, but surprisingly I can't find the solution through goggling, searching and keep trying. So I stuck.

I simulate phantomx arm (actually the model doesn't matters) to move it to desired position X,Y, Z. I can move the arm using Move Group Python Interface Tutorial when I set both position and rotation (7 values totally). This is fine when the end effector relative position doesn't change and I can calculate quaternion.

The issue starts when to reach some point (which is hight enough) I need to change the angle of end effector. Have a look on image illustration (sorry can't insert images)

I use Moveit! to find the joints values to reach the desired point, so I can't know beforehand the rotation of the end effector.

The question: Can I move my arm to the desired point without specifying rotation, just letting Moveit! to select any valid value as it does with other joints?

I have 2 ideas how to solve the issue:

1. Probably rotation constraints are solution, but tutorial is in C++ and I can do in python only
2. Add fake floating joint as an end effector, so that any rotation would be valid (because the joint is float it can take any values)

Please advice me the right way to solve the issue. I would be really really thankful because it is my headache now.

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