Originally Posted by JCS Help File Bundled With Game

Shift+E:
Put the active event to the tile under the cursor. This key also associates an event with the tile under the cursor, but it doesn't use the event selection dialog, it uses the active event instead. You can set the active event using the E or Control+E keys.

Ctrl+E:
Grab event under mouse cursor and make it the active event. First position the mouse over a tile with an event on it and press Control+E to grab that event as the active event. You can then use Shift+E to copy this event to other tiles.

Originally Posted by JCSref article "JCS Hotkeys"

SHIFT+E
This pastes the event that is currently active on the tile your mouse pointer is at. The active event is the last event you selected. For example, if you place a "fast fire" event on a tile the "fast fire" event is the active event until you select another event.
How to use?
Press SHIFT+E while your mouse pointer is at the tile you want to place an event on. You can click on the tile to make sure you selected the right one, but that's not needed.

CTRL+E
This makes the current active event the event that's currently under your cursor. It works like the "grab event" option you can choose from the drop-down menu that drops down when you right-click in the level window.
How to use?
Place your cursor on a tile with the event you want to choose on it. Then press CTRL+E. The event that was under your cursor is now set as the active event.