The device displays a messaging user interface on a display, the messaging user interface including a conversation transcript, a plurality of electronic stickers, and a message-input area. While displaying the messaging user interface, the device detects a first user input while a focus selector is at a first location in the messaging user interface that corresponds to a first electronic sticker in the plurality of electronic stickers. In response, the device places and displays the first electronic sticker in the conversation transcript. While the first electronic sticker is displayed in the conversation transcript: the device detects a second user input while a focus selector is at a second location in the messaging user interface that corresponds to the first electronic sticker in the conversation transcript. In response, the device changes the position, size, and/or rotation of the first electronic sticker in the conversation transcript.