Jevko may be the best general-purpose syntax for manual editing. This is thanks to its extreme simplicity and frictionlessness as well as human-readabiltiy. A manually edited Jevko document can be easily converted to and from another format of choice. For reading and writing Jevko, any text-editor will do. Even without syntax highlighting, Jevko is readable, with standard indent-based formatting. Jevko removes unnecessary redundancy, maximizing signal-to-noise ratio.
See also this related Mastodon post.