The bookmark bar is a very useful in providing quick access to your favorite websites. If not visible, then you need to enable it in your browser settings. For example in Chrome, click on the three horizontal dots (right side of browser), click on Settings then Appearance (on left) and make sure Show bookmarks bar is set to enabled (blue).
Many people have bookmarks in whatever order they have added them. However, particularly for the bookmarks that are visible on the bar it makes a lot of sense to arrange these in alphabetical order.
Why? Firstly, having them arranged in order makes them easier to find. A small reduction in cognitive friction but it all helps.
Secondly, in moving them you will often end up renaming them from the browser default - which is often long and uninformative - to something shorter and more meaningful. As a bonus, this means that more bookmarks are visible on the bar before disappearing out of view into Other Bookmarks.
Both are easily done (using Chrome as the example). To rename, right click on the bookmark, go to Edit and give it your shorter snappier name. To move, put your cursor on a bookmark, press the left button and while holding it down, drag it to its new location.