How to reproduce:
1. Create a new Unity project
2. Import the attached “text.cs” file
3. Create an empty GameObject Prefab
4. Add the “text.cs” script to it
5. Select the GameObject Prefab from the Assets folder
6. In the Inspector window, go to the Script component and double click on the “FirstString” part of the “FirstString.SecondString.ThirdString” text
7. Observe the selected text

Actual result: The entire string is selected
Expected result: Only the “FirstString” part is selected

Reproducible with: 6000.3.0a5(f9a1fab5607a), 6000.3.3f1, 6000.4.0b2, 6000.5.0a4
Not reproducible with: 6000.0.65f1, 6000.3.0a4

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

Note: Selecting any part of the “String1.String2.String3” works as expected