Reproduction steps:
1. Open user's project "ToggleEditorExceptionInPlaymode.zip"
2. Open "SampleScene" Scene
3. Enter Play Mode and click on "Toggle" under "Canvas" in the Hierarchy window
4. Try toggling the Toggle in Game View while looking at the Inspector window
5. Notice how the "Is On" field in Inspector is toggled as well
6. Try toggling the "Is On" field in Inspector

Expected result: Toggle in Game View is toggled when toggling the "Is On" field in the Inspector
Actual result: "InvalidOperationException: This cannot be used during play mode." exception is thrown when toggling the "Is On" field in the Inspector

Reproducible with: (using UGUI 1.0.0) 2019.2.0b4, 2019.4.0f1, 2019.4.19f1, 2020.2.3f1, 2021.1.0b4, 2021.2.0a3
Not reproducible with: (using UGUI 1.0.0) 2018.4.31f1, 2019.2.0b3

Note: on version 2018.4.31f1 toggling the "Is On" field in the Inspector doesn't toggle the Toggle in the Game View