Empty space in Ad-hoc sub-process (Stage), containing at least one node, is not used when putting new nodes in case view.

Current behaviour:

• A new node is still placed below the already existing node (not directly) in "y axis".

Expected behaviour:

• If there is a space for a new node, it should be added from the upper part of the ad-hoc sub-process to prevent wasting space.

Steps to reproduce (see pictures in the attachment):

1. Create ad-hoc sub-process in process view
2. Put User Task to the right side of the sub-process
3. Switch to case view
4. Put any node to created sub-process
5. Change order of sub-process's nodes
6. Switch back to process view