I have upgraded a project from 2019.2.10 to 2019.3.0b8 and in that project I had used EnumToggleButtons attribute to display some mutually exclusive enum choices in the inspector. I am using Odin 2.1.5 in both copies of the project, editor only mode is off, and I am on Windows 10 64 bit OS.
In 2019.2 the currently assigned enum value in the field was showing as selected correctly:
Now however in the newer Unity 2019.3 interface, the selected item (i.e. the TQ above) no longer appear highlighted even when clicking on that value again:
The Asc Size example above is also an EnumToggleButtons field that should be showing the first entry as selected but isn’t.
I don’t know if this is an issue with Odin or with Unity’s new interface, but it should be reproducible by testing an enum with the attribute on both versions of Unity.