Thank you for your answer. The first question is to put in "PASS" or "Low_confidence" in the "FILTER" column based on some filtering thresholds on QD and FS of SNPs and Indels. For single sample VCF, its easy, but for joint VCF, I want to put in the flag based on one sample in the joint VCF (for example child). But GATK VariantFilteriation is using the "INFO" column which in joint VCF, is a summary of all samples in the VCF.
I hope I made it clearly. Any suggestions?