Reproduction steps:
1. Create a new Unity project
2. Make sure that Unity Editor is not in full-screen
3. Drag the Unity Editor to the left side of the screen
4. Expand the Editor window to the right side
5. Observe the top right corner of the Toolbar

Expected result: The buttons in the Toolbar do not disappear when resizing the Editor
Actual result: The buttons disappear in the Toolbar when resizing the Editor

Reproducible with: 2019.3.16f1, 2019.4.0f1, 2019.4.35f, 2020.3.27f1, 2021.1.28f1, 2021.2.0a2
Not reproducible with: 2021.2.0a3, 2021.2.9f1, 2022.1.0b5, 2022.2.0a2

Notes:
- Issue is not reproducible on Windows
- In 2019.4.35f1 Unity version Toolbar becomes transparent, "Account", "Layers" and "Layout" buttons disappear
- In 2020.3.27f1, 2021.1.28f1, 2021.2.0a2 Unity versions "Account", "Layers" and "Layout" buttons overlay one another when expanding the Editor, eventually, buttons disappear
- Could not test with 2019.2 and earlier due to error when creating a new project: "Failed to resolve project template: [com.unity.template.3d] is not a valid project template."