Using a custom certificate and LetsEncrypt certificates on the same project?

Is it possible to use a custom SSL certificate just for a specific domain, and use the autogenerated one for all other domains on the same project?

If the custom certificate SAN/CN matches the custom specific domain, the custom certificate is preferred over autogenerated Let’s Encrypt certificates.
One exception is at the end of the custom certificate validity, where a Let’s Encrypt certificate is generated in the background to replace the custom certificate if it isn’t renewed.

If a wildcard custom certificate is upload, it will always be preferred for all domains matching the wildcard SAN/CN and not only a specific subdomain under the wildcard.