Event storming is not a notation
Event storming is not a notation. It's a very interactive team practice based on sticky notes put on a board and rearranged as the modeling progresses.
It starts with the identification of the events, seeks for the commands that cause them, and then looks at the involved aggregates/entities. And a couple of other things not directly relevant for your question.
The event stickers are arranged/rearanged according to an intuitive chronological order. Parrallel events are usually stacked vertically. When commands are added, the narrative gets some flesh and the flows tend after a while to stabilize. That's the moment some arrows can be added to better identify alternatives, parralel flows, and relations between distinct groups.
And the loop?
In event storming, there are no loops and no control flow. The backbone is made only of events. The loop is what emerges when an event is triggered that already appeared upstream, or when the same events repeat successively.
In addition, if you start to draw attention of participants on loops and control flows, you risk to glitch into a flowchart-driven thinking and miss the benefits of event storming.
Fortunately, there are intuitive practices with stickky notes, that help you keep the focus on the events, but yet capture these special loop situation without puting them too much in the fore ground. For example:
- put a comment note on a command to explain what happens .
- put a comment note on an event if a single event is repeating successively. Typically a 🔁
- use duplicate events. To avoid the risk of confusion, put a special symbol on the event sticker. This approach is consistent with the usual ES practices. When a duplicate is introduced or detected, it also highlights an area where care is needed.
If looping consideration appear at a later stage, you can of course simply draw an arrow backwards. But caution: If you start too early with arrows on the board, you might start to freeze the game: it becomes much more difficult to move the stickers. This may lead to less willingness to rearrange and ultimately creates friction in the free flow of ideas.