Which of the following is more idiomatic?
List out the groups you participate in.
List out the groups you're participating in.
Which of the following is more idiomatic?
List out the groups you participate in.
List out the groups you're participating in.
List out the groups you participate in.
This sentence would be more appropriate when talking about participation over a longer period of time. E.g., when inquiring about groups that the listener regularly participates in.
List out the groups you're participating in.
This sentence implies that the participation is either more short-lived, or will take place in the future (present continuous for future arrangements).
If inquiring about special interest groups at a learning institution that hold regular meetings, I would go with "List out the groups you participate in."
If inquiring about a single-day event with several groups that the attendees can participate in, I would go with "List out the groups you're participating in."
If inquiring about groups whose activities haven't started yet, I would go with "List out the groups you're participating in."