Hey there!
If Ultimate Stacker does not work, you could always try making a Skript for it!
Here >>
command /domino23:
trigger:
give 64 potions of swiftness to player
send "&cHere you go! Leave a 'thanks reaction on this post if I helped." to player
How to install Skript >>
Find the Skript plugin, and hit install.
Next, restart your server and head over to your file manager.
Now select plugins > skript > scripts > new file
Name the file to <nameofyourfile>.sk - the .sk part is very important!
Now paste my Skript into that file, hit save and go back into your game.
In game, type /skript reload <nameofyourfile> - without the .sk!
It should successfully reload and when you type the command /domino23, you should get a stack of swiftness potions.
I hope this helps you!
If it did please leave a 'thanks' on this post!