If I’m understanding your point correctly, HTTPie has support for multi-value keys in query strings.

You can use the `name==value` query parameter syntax [0]:

  $ http --offline pie.dev/get AAA==AAA AAA==BBB
  GET /get?AAA=AAA&AAA=BBB HTTP/1.1

Or simply:

  $ http --offline 'pie.dev/get?AAA=AAA&AAA=BBB'
  GET /get?AAA=AAA&AAA=BBB HTTP/1.1

[0]https://httpie.io/docs/cli/querystring-parameters