You will build the launchpad in the Level Editor, and then convert it to a Blueprint Class so you can add your gameplay behavior to it.
First, move around in the viewport until you are looking at the top platforms in the level.
We are going to create the container to hold all the parts of our launchpad by using the Empty Actor. The two parts (or Components) you will need are a shape to represent the launchpad, and a trigger for when the character
In the Modes panel, click on Basic, then find the Empty Actor.
Drag it into the level so that it is sitting on one of the top platforms.
Now that you have the Actor selected in the level, its properties are visible in the Details panel. At the top of the Details panel, you can rename it. Go ahead and click in the box to enter a new name, like LaunchPad.
The first component we are going to add is a cube, although we will scale it down a bit to make it more platform-sized. Adding this component first makes it the Root component, so all other components
will follow its lead for position, scale, and movement around the scene. You can rearrange components as you work, as well, so this is not a permanent decision.
In the Details panel, click the Add Component button, then select Cube under Basic Shapes.
Now you should have the Cube component selected, so you can tweak its properties. Resize the cube to (1, 1, 0.1).
Now, we will add a Box Collision Component, which will fire off an event whenever something overlaps it. In the Details panel, click the Add Component button, then select Box Collision under Collision.
Resize the box to be the size of the platform in X and Y, and extend a bit above the platform in Z. If you want to enter in your Scale directly, try (1.25, 1.25, 1.5).
If at any time you need to change your Actor's properties, such as to scale up the whole launchpad, you can click on LaunchPad (Instance) right under the Add Components button in the Details panel.
Now that you have your Actor the way you want it, we will turn it into a Blueprint Class. You can add more components inside the Blueprint Editor, and tweak them just like you can here in the level.