From the bug report , which also has a screen shot mock up "This would make it easier to identify the folders of diffrent mail accounts. This would also make sense for the top account nodes."
Great news. This is fixed by Bug 242300 - New/unread messages in thread are not obvious enough (bold vs. underlined) in a current release. And will appear in the next esr release 153 in a month.
With the core requirement delivered, I'll close this idea. No doubt more improvements can be made, so please submit new ideas to https://connect.mozilla.org/t5/ideas/idb-p/ideas/label-name/thunderbird
@il-Mimo,Your suggestion should be in it's own idea with a title suited to the request - please submit a new idea. And please clarify what you mean by "please consider expanding the size of the colour strip for calendar reminders so it has much great...
