Lokalise supports version 1.2 YAML files.
en:
app:
title: "Lokalise"
:yes: "Yes"
:no: "No"
bacon:
one: "1 bacon"
other: "{{count}} bacons"
When adding a new key via the web interface, use : to refer YAML levels, for example app:title. You can override the default separator (:) with a dot (.) in project settings > Advanced options.