I’ve spent hours looking for this option, whilst importing over 12GB of email data.
We have over 8 years of historical data, and important for us to review a client record, say post-op operation from 2002 folder (displayed on one screen), with data recorded within new active folder, on the primary screen (very fast way to X-REF).
I cannot see an issue with adding this, if not already available, as a majority of other email clients, it’s a standard feature.
Many thanks
Nick