You can simply modify the survey and publish it, and it will be available to all participants. When you want to publish the survey, you will be asked whether or not you want Ethica to send the new changes to all participants right away. If you choose yes, Ethica will send the app the new changes as soon as possible and participants get the changes you made. If you choose no, this won’t happen, but the changes still remain published, and participants will receive it gradually, with a delay, for example when a new participant joins, or a given participant goes to the app and chooses “Reload Studies from Server”, or they update their app. But unlike the first scenario, it won’t happen right away.
What you can do is to first join the study with a dummy account, so you get the current schedules, the make the changes, publish it, and ask not to notify participants immediately. Then update only your own account (as described here). This way you can check to make sure everything went well. If not, make changes as necessary. When you are comfortable with the changes, go to
Participation -> Adherence page and send an update to all participants, so they receive the changes right away.
Hope this answers your question