Toggle frontmatter in obsidian source and reading views.

Frontmatter.css

/* 
  Hide all frontmatter by default (can still view properties in right pane)
  To view/edit add `show-frontmatter` class to cssclasses or toggle with Snippet Commands plugin
*/

/* Hide frontmatter preview for reading view */
.markdown-preview-view:not(.show-frontmatter) div.metadata-container { 
    display: none; margin: 0px; height: 0px; visibility: hidden;
  }

/* Hide frontmatter in source mode - hide lines containing frontmatter markers */
.markdown-source-view:not(.show-frontmatter) .cm-line:has(.cm-hmd-frontmatter) {
    display: none;
    height: 0;
    line-height: 0px;
    margin: 0;
    padding: 0;
}

/* Hide entire frontmatter block including content between --- markers */
.markdown-source-view:not(.show-frontmatter) .cm-line .cm-hmd-frontmatter {
    display: none;
    height: 0;
    line-height: 0;
}

/* Also hide the fold indicator for frontmatter lines */
.markdown-source-view:not(.show-frontmatter) .cm-line:has(.cm-hmd-frontmatter) .cm-fold-indicator {
    display: none;
}

** Updated ** - made frontmatter hidden by default and added a class for showing in individual notes. This pairs better with the Snippet Commands plugin and pollutes fewer notes with cssclasses.