The Better Sort mod for Stardew Valley is a very helpful application that will help you improve the default inventory order and will also allow you to configure it to your liking. This mod also automatically stacks items in case you've spread your stacks out.

In addition, the Better Sort mod has a very useful function that allows you to right-click items and they will be automatically sorted according to the category that you have set in the configuration. You can also sort items the same way as the base game, but with added sorting for putting stacks in size order and higher quality items before lower quality ones.