How to use
you need to configure the plugin for the blocks you want to stack, use the config.yml command or /setmaxstacksize
after which, drop and pick up Item to stack them

/setmaxstacksize <number> command
config.yml:
Settings:
Groups:
Items:
I added similar blocks as beds of different colors in groups for easier customization. Set default if you don't want the plugin to touch them.
Or the Number to which they will stack.
Items : you can add blocks that you want to stack
blocks in Items take precedence over blocks from groups, so you can make all the beds stack 64 and the red bed stack 1


How it works:
StackOptimized is a very small plugin that makes your life easier, it is highly optimized and hardly loads the system, it never loads your server up to 0.1%. in most cases it doesn't do anything, all the mechanics of stacking items minecraft does by itself. It only changes an item's data when the player picks it up, after which the items begin to stack.