Repro:
1. Create a new project using 2019.2.0b8
2. Download the LWRP package via the Package Manager window
3. Create a LWRP asset and assign it as the active render pipeline
4. Create an Unlit Shader Graph
5. Open the newly-created Shader Graph
6. Press space and click outside the node menu
7. Press space again and Color Picker should open
8. Press space and create Blend node
9. Press space and click off node menu. Repeat several times
10. Try moving any of the nodes