The alternate allele in the VCF is expressed as a sequence of one or more A/C/G/T nucleotides. According to the VCF 4.1 specification, symbolic alternate alleles is used for imprecise structural variants (e.g. <DEL>, <DUP> and so on). I'm working with manually generated VCF files. So i'm interested is it possible to use symbolic alternate alleles for long deletions/insertions with known breakpoints? And if it's enabled, is there are any recommendations on the minimal variant length for using a symbolic alternate allele?