Describe the bug
Originally the new header mode toggle @youknowriad added in #18624 was labeled Navigation Tools, but that heading was removed. The remaining description prominently labels them as Tools, while Tools already exists under the Main Menu for a disparate set of features.

Additionally, adding this item to the header means there are now six items users viewing the interface need to parse, which moves from the top-end of the perceptual subitizing scale into conceptual subitizing that requires additional cycles to subdivide. Depending on age and cognitive function, humans can identify up to five like items without counting, with six or more like items almost every brain must sub-divide items into smaller groups to compute the whole.

Expected behavior
At minimum the confusing double-use of Tools should be addressed. This could be as simple as relabeling or adjusting the descriptive text.

A few ideas...

• New Control Type - It appears the two Modes are intended to be a binary, similar to Visual/Code Editor. One way to address the clustering of buttons could be to use a Toggle Control with edit as the active state and select as the inactive state. Tooltips and Snackbars could explain the mode switch to users.
• Combine Outline/Inspector - The Content Outline and Block Inspector could be combined under a unified button with a tree icon, the counts could be at the top and the bottom section could use a TabPanel to toggle between the Outline and Block Inspector.
• Relocate Outline/Inspector - The Outline/Inspector could relocate into the Editor Footer region, prefixing the Block Breadcrumbs. This would keep Header buttons to be tools that take actions like the Block Inserter, Undo/Redo and Edit/Select toggle, where the footer could be tools that define context and aid in navigating a document.

Screenshots