(I'm posting this as an answer instead of a comment to the moderator's answer to have enough space to elaborate on my perspective.)
I respectfully disagree with the decision to close this question as off-topic and migrate it to Super User. I think this decision may have been based on an assumption that wasn't supported by evidence. As I mentioned earlier in the meta post about Facebook users switching to mobile apps, we should give the benefit of the doubt to the OP and assume they are asking about the web app, unless they explicitly state otherwise or mention something exclusive to the mobile or desktop app.
the question doesn't include any hint about what platform is used.
If a question clearly refers to something applicable only to the desktop or mobile app and irrelevant to the web app, then closing it as off-topic and migrating makes sense. However, in this case, the screenshot OP provided seems to be from the web app (which looks very similar or identical to the desktop app).
Discord is primarily intended for use with an installable client.
I don't think the developer's intention should determine whether a web app is on-topic here. Many other web apps, like Facebook and Instagram, are primarily meant for use with a mobile app, yet questions about their web apps, accessible from a web browser, are still considered on-topic. Unless Discord discontinues allowing access from a web browser, questions about its web app should remain on-topic for Web Apps SE.
Let's give the asker the benefit of the doubt and assume they're asking about the web app, unless they clarify otherwise. If that's the case, I believe this question is considered on-topic for Web Apps SE and should not have been migrated.