If you are using electronic timing and want to synchronize/upload it to Athletics.app, Athletics.app will always assume that this is the result for "attempt 1".
This means you cannot upload multiple attempts from the ET.
For Athletics Champs you also have to take the heat format into account: Athletics Champs does not have a pre-determined heat format. Each team occupies one lane and sends their athletes out from there. One team has eight athletes, the other team has 11. After eight heats, the first team is already ready for their second attempt, while the other team still has three athletes who are doing their first attempt. So you have constantly changing heats.
This has been automatically translated into English