How to reproduce:
1. Open the attached project “SearchHDRP.zip“
2. Open the Project Settings window (Edit > Project settings…)
3. In the search bar of the Project Settings window, type “water”

Expected result: All options with the word “water“ show up and are highlighted
Actual result: Only one option with the word “water“ shows up and isn’t highlighted

Reproducible with: 2020.3.41f1, 2021.3.13f1, 2022.1.22f1, 2022.2.0b12, 2023.1.0a16

Reproduced on: macOS 12.5 (Intel)

Note:
- To test the issue in 2020.3, 2021.3, 2022.1 Unity versions, search with the word “intensity“ to reproduce the issue
- When searching with the word “radius“, it doesn’t show all results if you type “radius“, but it does show if you type “radi“

In this case we would like the "header" to be higlighted. It seems the header in that case doesn't use the PrefixLabel mechanism.