Reproduction steps:
1. Open the attached “TextMeshProReferencing.zip” project
2. Select the “NewAssembly.asmdef” in the Project Window
3. Find to the the “Assembly Definition References” field in the Inspector
4. In the “(Missing Reference)” property click on the circle to select a reference

Expected result: Unity.TextMeshPro.asmdef reference option is available
Actual result: Only the NewAssembly.asmdef reference option is available

Reproducible with: 2021.3.38f1, 2022.3.20f1, 2023.3.0b4, 6000.0.1f1
Not reproducible with: 2022.3.29f1, 2023.3.0b3
Fixed in: 2022.3.21f1, 6000.0.2f1

Reproducible on: Windows 11
Not reproducible on: No other environment tested

Note:
- “Assets\text.cs(5,30): error CS0246: The type or namespace name 'TextMeshProUGUI' could not be found (are you missing a using directive or an assembly reference?)” and “Assets\text.cs(2,7): error CS0246: The type or namespace name 'TMPro' could not be found (are you missing a using directive or an assembly reference?)” errors are also thrown in the Console