The SEO tab is three text fields, repeated for each language your group has enabled. Almost everything else search engines need - the sitemap, the canonical URL of each page, telling the search engines a page changed - the platform handles without asking you.
SEO in the group settings lets you override the site-wide meta descriptions for your groups domain. A meta description is the grey line under the blue link in a search result: it does not affect ranking, but it decides whether someone clicks. A row of language buttons sits above the fields, one per active language, and the counter at the top reads how many of the whole set you have filled in - two languages means six descriptions. Leave a field empty and the platform default is used, so the tab is safe to ignore until you have something better to say.
Each group's domain gets its own sitemap, listing that group's pages and events, which is what a crawler reads to discover them. Every page also declares a canonical URL, so the same event reachable through two addresses is not counted as two pages competing with each other. And when content changes, the platform can tell the search engines directly through IndexNow instead of waiting for the next crawl. None of the three has a control on this tab - they are the platform's job.
Say what the group is, not that it is a group
"Monthly film nights in Berlin, subtitled and open to newcomers" beats "The website of our film club".
Put the specific words first
The place, the topic and the language your meetings are in. These are what people actually type into a search box.
Stay under 160 characters
The field enforces it, and a search result truncates around there anyway. Write the important half first.
A description is not a ranking lever
Search engines routinely ignore the meta description and write their own from the page. Treat these fields as your best offer, not as a setting that controls anything. What actually moves a group up the results is having real content in the language people search in.