AWS console doesn't show security groups from peered VPC. But that doesn't prevent you from manually copy pasting the ID of source security group from requester VPC.

Just manually copy paste the source SG id and it will properly allow requests from requester VPC attached with this source SG.

This is just AWS Web UI not supporting pre-population of security groups from peered SG. But that doesn't mean it won't work if you manually put the value.