To keep the information centralized, if you are view this page from curseforge site you can view/post messages from bukkit project page: https://dev.bukkit.org/projects/clicksort-lite
This plugin sorts and organizes inventory contents automatically just by middle click it, it is inspired in Inventory Tweaks Mod and ClickSort plugin, but lighter and with craftbukkit 1.13+ support

before middle click (images are referencial)

after middle click, items are automatically sorted and stacked (not shown in the image)
Just open the chest/inventory and middle click inside, it will sort contents alphabetically and stack items to save space
Any inventory with "container" slots which include:
Just copy/move the jar file inside the server plugins folder and reload/restart the server
if you found some bug try to isolate the problem first and find/resolve the cause, in mostly cases could be a conflict with other plugin
if the problem persists report your findings in https://github.com/atesin/ClickSort-Lite/issues, including server logs, detailed steps to reproduce your environment/problem and your compressed server folder (excluding world subfolders and sensible information)... make it me easy because i currently dont have the time and energy to do much researching
Thanks for your interest in this plugin, but please don't request exotic features like item classification, partial sorting, sort multiple chests, etc... i'm not so skilled in java and my time is limited too
I write plugins with simplicity on mind, to add features that i think will be useful in vanilla minecraft, and share the code to help others to learn java like me
If you want a feature you can search another better plugin, examine the code and submit a patch, or start a fork (please respect the license)