A simple gem to work with rails_admin that allow you to choose element in a tree.

gem "rails_admin_tree_browser"

Then, add in your rails admin model initializer
config/initializers/rails_admin/modelName.rb

RailsAdmin.config do |config|
  config.model MyAwesomeModel do
    edit do
      field :db_path_field, :tree_browser do
        tree_root_url 'https://url_to_api_return_json.com'
      end
    end
  end
end

• tree_root_url - The root url from where we show the tree
• tree_download_url - the download url from where we download the element, need to be download_link to true (Optional)
• download_link - true/false Show icon with link to download (Optional)
• button_label - Overwrite the label name (Optional)
• node_type_name - overwrite de node type name, default: node (Optional)
• element_type_name - overwrite de element type name, default: element (Optional)

example:

RailsAdmin.config do |config|
  config.model MyAwesomeModel do
    edit do
      field :path, :tree_browser do
        tree_root_url 'https://url_to_api_return_json.com'
        tree_download_url
        button_label 'Choose a file please'
        download_link true
        node_type_name 'dir'
        element_type_name 'file'
      end
    end
  end
end

example for https://url_to_api_return_json.com/node

[{
name: "element",
path: "node/element",
type: "element"
},
{
name: "sub_node",
path: "node/sub_node",
type: "node"
}]