Panels

Two panels sit beside the document: a files sidebar on the left in folder mode, and an outline of the headings at the top right. Both are trees, fold the same way and share the same keys.

Open a folder and its Markdown files appear in a sidebar headed by the folder's name, with the tree hanging from it. Folders come first, the open file is highlighted, and connectors show the nesting.

Files are found with the same rules as ripgrep: .gitignore is honoured, even outside a git repository, and hidden files are skipped.
The extensions counted as Markdown are md, markdown, mdown, mkd and mdx.
mido starts on README.md, then index.md, then the first file in the tree.
T shows each file's first heading instead of its name.
The whole tree is watched. Files that appear or disappear on disk show up in the panel with the folds preserved.

b toggles the sidebar. It takes a quarter of the terminal width, between 22 and 32 columns.

Outline

The headings of the current document sit in a rounded, tinted card at the top right. The text wraps before it rather than running underneath. The card is as wide as the longest heading, at most 32 columns and a third of the screen, and as tall as its visible rows.

The section that contains the top of the viewport is highlighted, and if that heading is inside a folded section the folded ancestor is highlighted instead. o toggles the card.

Folding

In either panel:

Key	Action
`j` / `k`	Move up and down
`Enter`	Open the file or jump to the heading, and return to the document
`Space`	Fold or unfold the row
`←`	Collapse, or move to the parent
`→`	Expand
`-` / `=`	Fold everything / unfold everything

Long entries wrap onto continuation lines instead of being clipped, with the tree guides carried down through them.

Focus

Tab cycles focus through the files sidebar, the document and the outline, in that order, and wraps around. Shift-Tab goes the other way. An arrow key pressed right after Tab moves in that direction instead. l moves to the pane on the right.

The focused panel shows its border or rule in the accent color. Enter or Tab from a panel brings focus back to the document, and so does clicking a file or a heading. Clicking a folder or a fold marker leaves focus on the panel.

Focus mode

f hides both panels and gives the document the full width. Press it again to restore them. b or o also leave focus mode and show that one panel.

Narrow terminals

Panels appear only while the document keeps at least 60 columns. On a medium-width terminal the files sidebar wins over the outline. Forcing a panel on with b or o lowers the limit to 40 columns. Below that the document has the screen to itself.