Streamlit's default sidebar section header uses a Material Symbols
expand_more chevron — three different icons (chevron down, chevron up,
sometimes a plain triangle) depending on version, all of which felt
inconsistent with the rest of the chrome.
Hide the built-in icon (svg / material-symbols span — covered with
multiple selectors for cross-version durability) and render our own
glyph as a right-aligned pseudo-element on the section-header button,
keyed off the standard ARIA aria-expanded attribute:
- collapsed → "+"
- expanded → "−" (U+2212, visually balanced with +)
Hover deepens the indicator color to match the surrounding nav-link
hover treatment.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Michael
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