Yes, that makes sense, and you’re pretty close to what you want. The nice thing about link fields is that they essentially work two ways. When you create a link field in [Table A] pointing to [Table B], Airtable makes a matching field in the “target” table (B in this case) so you can see the incoming links from A, but the link isn’t a one-way street. With that link in place, you can create a new link in B pointing to a record in A, or the other way around.
In your case, you’ve linked your [Projects] and [Participants] tables, and have connected participants to specific projects. However, that same link allows you to work from the [Projects] table and add links to records in [Participants] just as easily.
So now let’s look at your goal:
Because of this link between tables, you can now add certain field types that specifically operate on linked fields. In this case, you want the number of participants linked to a given project. One of Airtable’s link-driven field types is the Count type, which does nothing more than count the number of links in a specific link field. By adding a Count field—named something like {# of Participants}—to your [Projects] table, and setting it to count links in the field connected to your [Participants] table, each project record in [Projects] will show its own participant count.
