If you'd like only to track a subdirectory (or folder) of your website to analyze the organic traffic, a couple of options can do the trick.

The first option is to create a custom segment in the Organic Traffic module. You can filter the organic traffic based on the landing page rule, like in this example, where you will see traffic coming from landing pages containing "/blog/."

On top of this, you can create a smart group with the same rule, to only look at the keywords you're tracking that are triggering landing pages containing "/blog/."

Moreover, this group can then be individually analyzed in the "Competition" tab as well, with its specific competitors.

The second solution can be to track the subdirectory separately and add it as a new campaign. Still, you'd need to have its separate GA and GSC profiles or a filtered GA view and a separate GSC profile.

If this is the chosen option, remember that the ranks you will see will still be for the main domain and not the folder.