Tested Unity version: 2019.3.0a12 (856a59fec312)
Does not reproduce in Unity version 2019.2.1f1, Shadergraph version 6.9.1
How to reproduce:
1. Create a new project
2. Add Universal RP package to the project (7.0.1)
3. Create a new shadergraph file and open it
4. Create a "Input > Basic > Vector 1" node
5. Create a "Math > Round > Step" node
6. Plug the "Out" of the Vector 1 node into the "Edge" of the Step node
7. Minimize the step node (the downwards arrow on the upper right of the node)
8. Un-Minimize the step node

Expected behavior: the input value section of the node should remain usable
Actual behavior: the input value section of the node (to the left of In(1)) will become clipped and be impossible to use until the Shadergraph window is closed and re-opened (see image)

Notes: This problem does not only happen for the Step node, it happens with almost any node with multiple inputs, after plugging something into one of the inputs and then minimizing and maximizing.