The first thing you need to understand is folders are hierarchical. SO if you click the widget on the end of the list of folder heading and choose the apply changes to item at the end, you can apply the changes to children. That is folders that are children of the one you are modifying. You might also want to apply a global sort use the view menu (alt+V). Do not use the view menu under the three line hamburger on the toolbar. For some reason some items appear permanently disabled on it. Select view sort by and make some choices as to sort orders. The first thing I did on getting Thunderbird was switch sort order so new mail appeared at the top.