Hi jwd et al,
The trouble with Tiddlywiki is that it's so hard to say just what a "casual user" should and shouldn't be able to or be expected to do.
All the core UI is written in wikitext, so it can be changed if you want to, but you have to understand how it was built in the first place. Ironically, if the UI is constantly expanded to incorporate ever more settings and options then the underlying wikitext gets progressively harder to understand.
To address the "annoyance/burden" that you are dealing with, I would suggest adding new UI (easy) instead of changing what's in the core (hard).
Put a new tab in the sidebar (by tagging a tiddler with $:/tags/SideBar) and put a list in it with a filter that matches what you want - perhaps [!sort[modified]limit[20]] or something similar. You can position it relative to the other tabs by giving it a list-before or list-after field and you can change the tab title by giving it a caption field. Then use this tab as your default.
If you want to remove the original 'recent' tab from view, open it ($:/core/ui/SideBar/Recent) and delete its tag.
Regards,
Richard