How to reproduce:
1. Create a new Unity project and import the "MySimpleGraph" Script
2. In the Project window, right-click -> Create -> Graph Toolkit Samples -> Simple Graph -> Open the Graph
3. In the Blackboard, create a few Variables
4. Select the first Variables and press "Ctrl +D"/"Command + D"
5. Observe the results

Expected results: The duplicated Variable appears directly beneath the original Variable, which is a standard behaviour across the Editor
Actual results: The Variable gets pasted at the end of the list

Reproducible with: 6000.4.0b7, 6000.5.0a6

Reproducible on: macOS Tahoe 26 (M1)
Not reproducible on: No other environment tested

Note: VFX Graph previously had the same issue