I have set up two tab groups (one for left lister and one for right).
I opened the recent.osd file whilst DOpus was starting after a PC reboot (I just started VS Code). As soon as DOpus came up, the recent.osd file populated itself with my default tabs.
Also, the two listers do not always remain in sync with the drop-down list on the Location Bar.
I've just increased the number of recent files to 20 and restarted DOpus, and whilst the list now shows some of the visited folders amongst the default tabs, there are still only 10 entries in the list. The recent.osd file has 18 entries.