Selecting a text field that is displaying "Multiple Values" will rewrite all values for all selected entities to "Multiple Values".
Reproduced in 4.7.6, 4.8.0, and Main (//depot/UE4/Promotable-CL-2585362)
1. Open any project
2. Create a new Actor Blueprint
3. Add a new Physics Constraint component, C1
4. Add another new Physics Constraint component, C2
5. In C1, set Component Name 2 to A
6. In C2, set Component Name 2 to B
7. Select both C1 and C2
8. Set Component Name 1 to X
9. Hit tab to jump to the Component Name 2
10. Select only C1
Both C1 and C2 have had the Component Name 2 set to "Multiple Values" when only one is selected.
Simply selecting the Multiple Values text in a text field does not set the value for all selected entities to "Multiple Values"
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