This is just one feature of the v3.6 release:

https://iterm2.com/downloads/stable/iTerm2-3_6_1.changelog

It's quite a treat going through iTerm changelogs and finding new gems. For example, this sounds nice:

> [Timestamps] can be configured to be relative to a particular line by right-clicking and selecting "Set Baseline for Relative Timestamps"

The following is interesting too, because it seems to work on an individual cell basis and not just one overall background colour:

> [in editors and other TUIs] Detect when there is a non-default background color and extend it into the margins. In Minimal [theme], it is also extended into window chrome.