GSC things

Could someone explain how GSC shows traffic from pages that aren't indexed and have filter symbols like "?filter"? Over 100 pages are getting only 1 click and 1 impression. How is this possible if they are not visible in the SERP? All of these pages have a canonical tag pointing to the product page without the "?filter".

Could they have been temporarily indexed? Should I block them with robots.txt?

Pages with query parameters like "?filter" might have been temporarily indexed by Google. During this period, they could appear in search results, generating impressions and clicks.
Even if a page has a canonical tag pointing to the main product page, Google might still index the URL with the query parameter temporarily. The canonical tag is a suggestion, not a directive, and Google may not always respect it immediately.

Google Search Console may report traffic for non-indexed pages with "?filter" parameters due to temporary indexing or relevance in specific search queries. Even with a canonical tag, these URLs can still generate clicks. Use `robots.txt` to block unwanted pages, but first ensure the canonical tags are correctly implemented and explore parameter handling in GSC to manage how these URLs are treated.

Pages with "?filter" may be indexed temporarily, check on GSC for any indexing errors and check whether the canonical tags are implemented correctly