Display mCNVs in the browser

[ch-kr]

This is a request to display multiallelic CNVs (mCNVs) in the browser. A user from DECIPHER pointed out that we don't appear to be displaying this variant type, flagging this variant as an example: gnomAD-SV_v3_CNV_chr1_0a6c7abe (from gs://gcp-public-data--gnomad/release/4.1/genome_sv/gnomad.v4.1.sv.sites.vcf.gz). I confirmed this variant isn't being displayed in this region: https://gnomad.broadinstitute.org/region/1-16682880-16682920?dataset=gnomad_sv_r4.

Per this slack thread, the evidence for mCNVs should be "RD" ("Read Depth")