Minecraft – How to duplicate things on laptop

You can use either the mouse scroll wheel (or scrolling sections/gestures on a trackpad) or the number keys 0-9 on your keyboard to switch between currently selected items in your hotbar. These are the main methods of doing so.

The "Pick Block" key is by default bound to your mouse Button 3, or the scroll wheel. Since many laptops do not support clicking with the scrolling function, you can bind the control to another key on your keyboard instead.

What Pick Block actually does allows you to quickly switch to another block type if you have it in your quickbar. For example, let's say you have some stone in your hotbar. If you use Pick Block on a stone block in the world, it will quickly swap to have that item selected.

Alternatively, using Pick Block in creative mode will automatically bring that block into your hotbar, if it's not already there.

Assuming you are in Creative Mode (as stated in your question), you can use the Pick Block control (defaults to middle mouse button) on the Firework Rocket item and you will get an extra 64 of it.

This doesn't only apply to Firework Rockets. You can clone any items with this key. You will get the maximum stackable number of that item (64 on most items, 16 on some others and 1 on armors/tools/etc).

Any properties (e.g. damage levels, fireworks, enchantments, potion effects, written books, etc.) will be cloned.