It appears the Sonar UI has changed in Sonar Cloud, making it harder to identify which code added in a PR to an existing file is covered by tests. The UI now only shows red markers in the side, without indicating whether a line was introduced in the current PR. Earlier, newly added lines were clearly highlighted with a white background, which made this distinction obvious.
For example, Sonar is showing Uncovered Code like below
Just to complete the thread, so that it may help someone in the future. The light white background is showing up in the Sonar UI where lines that are touched in a PR.