When adding multiple domains for some of domains cloudflare says:
We were unable to scan your domain’s DNS records successfully.
and so the DNS records for those domains remains with no record.
Is it possible to define default dns records to cloudflare use them in such case that can not scad dns records of domains?
If no DNS records were found, you will need to add them manually (you should check with your host if you are not sure what to add, they are often visible in your hosting control panel), this guide explains about Adding DNS Records
You mean default to scan or default to set up? Anyhow, I am afraid the answer would be in either case a disappointing “no”