The multi select filter renders checkboxes for a given list of options, hence allowing the user to select multiple values.

See the following example for an implementation of a multi select user filter.

defmodule MyAppWeb.Filters.MultiUserSelect do
  use Backpex.Filters.MultiSelect

  @impl Backpex.Filter
  def label, do: "User"

  @impl Backpex.Filters.MultiSelect
  def prompt, do: "Select user ..."

  @impl Backpex.Filters.MultiSelect
  def options, do: [
    {"John Doe", "acdd1860-65ce-4ed6-a37c-433851cf68d7"},
    {"Jane Doe", "9d78ce5e-9334-4a6c-a076-f1e72522de2"}
  ]
end

use Backpex.Filters.MultiSelect

When you use Backpex.Filters.MultiSelect, the Backpex.Filters.MultiSelect module will set @behavior Backpex.Filters.Select. In addition it will add a render and render_form function in order to display the corresponding filter.