Feels like VSCode or Obsidian, the majority of the window will be editor, showing only one tiddler at once, no card flow. To focus on one long text editing.
But might also need a sidebar showing filtered titles, to switch between reference materials.
Basically it will looks like https://bear.app/
One simple approach is a modified open in new window button that puts a tiddler in edit mode. But look around I have seen a full screen editor before.
I have shared a button for this in the past.
It maybe better to keep stay in the same window. But this approach may work too.
I will share the full screen editor if I find it when back at my desktop.
These are the two ones I know of
Multicolumn plug in also has a fullscreen view-toolbar and edit-toolbar button
