jake.stookey

This plugin ensures that all posts will always be in the default category. Whenever any post is saved, all posts not currently in the default category are put in the default category. For example, by renaming the default category ‘All’ you always have a category containing all posts.

All Posts Default Category

Ensures all posts are always in the default category.

Robert Noakes

Adds functionality to collapse and expand nav menus within the WordPress admin. All parent nav menu items are collapsed by default, but you have the option to store the collapsed/expanded state for the menus on a user-by-user basis.
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Nav Menu Collapse

Simple, to the point, this should absolutely be in core.

Adds functionality to collapse and expand nav menus within the WordPress admin.

All Posts Default Category vs Nav Menu Collapse