fixed-width fonts and ligature preservation in edit mode

mono_edit.css

:root {
    --font-monospace:                       "MonoLisa", "JetBrains Mono", "Consolas", monospace !important;
    --font-family-preview-edit-code:        "MonoLisa", "JetBrains Mono", "Consolas", monospace !important;
    --text-family-inline-code:              "MonoLisa", "JetBrains Mono", "Consolas", monospace !important;
    --rb-indent-font-family:                "MonoLisa", "JetBrains Mono", "Consolas", monospace !important;
}

/**
 * Use fixed-width font for edit mode
 */
.cm-s-obsidian,
.cm-s-obsidian .hmd-fold-html kbd,
.cm-header,
span.cm-strong, span.cm-em,
.markdown-preview-view :not(pre) > code,
.markdown-preview-view pre,
.markdown-source-view.mod-cm6 .cm-scroller,
.cm-hmd-list-indent .cm-hmd-list-indent-1,
.markdown-preview-view.is-readable-line-width .markdown-preview-sizer,
.markdown-source-view.is-readable-line-width .CodeMirror,
textarea {
    font-family: var(--font-monospace) !important;

    /**
     * Preserves ligatures regardless of theme (e.g. Blue Topaz).
     * Any value other than 'normal' disables ligatures.
     */
    letter-spacing: normal !important;

    /**
     * MonoLisa script italics
     */
    font-feature-settings: "ss01" 1, "ss03" 0, "ss05" 1, "ss06" 0, "calt" 1, "ss02" 1, "zero" !important;
}

/**
 * Disable small font for header prefixes in Blue Topas
 */
div.CodeMirror-activeline .CodeMirror-line span.cm-formatting.cm-formatting-header,
div:not(.CodeMirror-activeline)>.CodeMirror-line span.cm-formatting.cm-formatting-header {
    font-size: 1em;
}

CSS contortions, during which we preserve fixed-width fonts and ligatures in edit mode

I prefer monospace fonts for edit mode - both classic and live preview - especially monospace fonts with ligatures: MonoLisa, JetBrains Mono, FiraCode (in ❤️ order). As some themes (looking at you Blue Topaz) blow up ligatures with their pixel-tweaking, I've settled on this CSS snippet to ensure monospace ligatures are working.

This works with a number of Obsidian themes, including Default, Blue Topaz, and Nord.

Updated to enable MonoLisa script italics https://gist.github.com/pmbauer/42d67769c419ebf799938db62b1671bf#file-mono_edit-css-L30-L33 (credit TokyoMike on OMG Discord)