You installed plugins that add buttons to the toolbar, and then you shrank the item pane such that there's no space for the search bar. The minimum width of the pane doesn't account for third-party buttons, since we don't have anything to do with those.

In the future, we'll likely add an official way for plugins to add toolbar buttons, and at that point the toolbar would be able to dynamically adjust (e.g., by collapsing excess buttons into an overflow menu).