As I already commented, Z-index is not a shape property. A new object is created over all existing ones. By default, the oldest object is in the back and the most recent at top. You can use the
Arrange commands to modify this default order in a relative way (relative to a group of selected objects; you can’t send an object to the absolute 17th slot).
From experiment, a copy of a group of objects keeps the relative order of creation. Consequently, there is an obvious imperfect workaround. It works if you copy boxes with their connectors.
The group must be created in this order:
draw the connectors first
It does not matter if the connectors are not attached, you’ll do this later. The important point is the Z-index of the connectors.
draw the boxes and add the center glue points
select the connectors one by one and attach them to their glue points on the boxes
This is imperfect because you’ll likely need to add another connector between the group copy and the rest of the graph. This extra connector will need to be manually sent to back. However, this may decrease the number of manual steps.
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