How to assign LD proxy

When we use local data using TwoSampleMR, how can we assign LD proxies where the outcome data is not available?

https://mrcieu.github.io/TwoSampleMR/articles/outcome.html

  outcome_dat <- read_outcome_data(
   snps = bmi_exp_dat$SNP,
   filename = "gwas_summary.csv",
   sep = ",",
   snp_col = "rsid",
   beta_col = "effect",
    se_col = "SE",
  effect_allele_col = "a1",
   other_allele_col = "a2",
  eaf_col = "a1_freq",
  pval_col = "p-value",
   units_col = "Units",
  gene_col = "Gene",
  samplesize_col = "n"
  )

When we use "extract_outcome_data", we can automatically assign LD proxies, but this cannot be applied to local data.

   chd_out_dat <- extract_outcome_data(
    snps = bmi_exp_dat$SNP,
    outcomes = 'ieu-a-7'
    )
#> Extracting data for 79 SNP(s) from 1 GWAS(s)