preferring to not show the sidebar in expanded save dialogues

— image from Mac OS X Human Interface Guidelines: UI Element Guidelines: Windows: Dialogs: Save Dialogs

Question

How can I prefer to not show the sidebar whenever an expanded dialogue drops down?

Is there a relevant .plist somewhere on disk? (I'm familiar with the defaults command.)

Workarounds

Frequently repetetively manually drag the sidebar divider, every time the dialogue drops down. This is tedious.

Less tedious but still undesirable:

1. alongside FAVORITES, click HIDE
2. manually drag the divider towards (but not beyond) the edge of the word FAVORITES, to create a sidebar with a sane width
3. repeat occasionally (the preference does seem to be lost, but I haven't figured out the point at which loss occurs).

Observation

Keyboard shortcut alt/option-command-s (effective in Finder) is not effective in the dialogue.

Reasons for preferring to work without the sidebar at this time

Because 10.7 (Build 11A511) very frequently loses the vast majority of my favourites from the modern sidebar FAVORITES, I

prefer to use ~/Library/Favorites without the sidebar

• that bug affecting the sidebar is known to Apple
• details of my ~/Library/Favorites workaround might be posted to a separate topic.

Any long string (for example: a folder or saved search with a long name) seems to cause the sidebar to expand to the width of that string, intruding too far into the space that I wish to use.

And so on …