In Actions tab, Rotation value in UV Editor is not constrained to 360 which causes the Rotation slider handle to disappear, only on modifying the same rotation slider value with the help of the "Rotate" tool in the UV Editor. And it appears back when stop rotating the UV Handles of Rotation Tool.

Steps to reproduce :
1. Create a new project.
2. Window > Package Manager > ProBuilder > Install
3. Tools > ProBuilder > ProBuilder Window
4. ProBuilder >New shape (Cube)
5. ProBuilder > UV Editor > Enable "Face Selection" tool > Select any Face of Cube.
6. Actions tab > Modify "Rotation" value by sliding the slider handle (Set to 140).
7.UV Editor > Enable the "Rotate" tool > rotate the selected face using the UV Handles of Rotate Tool.

Actual Result: Slider handle of "Rotation" value disappears.

Expected Result: Slider handle of "Rotation " value is visible.

Tested on Unity version:
2020.1.0a18, 2019.3.0f5, 2019.2.17f1, 2018.4.14f1

Package version occurring: 4.3.0-preview.1, 4.2.1, 4.1.2, 4.0.2, 3.0.0

Environment: Windows 10 and macOS 10.14.