There seems to be a minimum size for the right portion of the window. If your window is too small it won't allow expanding the left panel. Is this possibly your issue.

Yes, this is the problem. I have a 1024x768 screen.

I've been using Evolution on a 1024x768 screen for a while now.  But I'm old, and my eyes get tired, so I've had to change my resolution to 800x600.

Don't laugh.  This problem *really* affects usability.

Anyway, I did the little "trick" about resizing the main window from the right side (so that much of the right-hand side of the main window is actually off-screen) and this made it possible to resize the left pane to a usable width.

However, when I exit and then restart Evolution, the main window resizes to only the desktop size, and the left pane (folder view) is again unusable until I repeat the previous steps.

I get that there is a "minimum size" for the right-hand portion of the main window, but currently it is just too wide to be easily usable by people with old eyes.

lane

Created attachment 227727 [details] [review]
evo patch

for evolution;

This makes EShellSearchbar descendant of GtkGrid (used to be a descendant of GtkBox), and makes it wrap-able, thus the three groups of widgets (in mailer, other views has only two groups) can be wrapped to more lines. It still has some minimum width, but it's approximately 1/3 of the "before patch". other option was to not wrap at all, just hide right-most widgets from the view, but it would look more like a bug than a feature.

I also removed unnecessary hack around e_shell_view_get_size_group(), which made more trouble than gain with the wrapping.

Created commit 9e64b59 in evo master (3.7.2+)