Nice work on this, @jensenpat — the four visualizations are a solid addition and the drawer keeps the default footprint compact. The refactoring of the paint path into separate drawGraph/drawEnvelope/drawBars/drawVerticalBars methods is clean, and the Goertzel-based frequency band analysis is a nice approach for the Bands view.

A few things worth addressing before merge:

1. AppSettings::save() on every slider tick

The zoom and FPS sliders connect QSlider::valueChanged directly to a lambda that calls settings.save(). Since GuardedSlider doesn't debounce, dragging either slider writes the full XML settings file to disk on every single tick. At 500 steps across the zoom range that's a lot of atomic write-rename cycles during a drag.

Suggested fix: Either connect to QSlider::sliderReleased for the save (keeping valueChanged for the live preview), or use a short QTimer::singleShot debounce so the save only fires ~200ms after the last change. The setValue + live update on the waveform is fine on every tick — it's just the disk write that should be deferred.

2. setZoomWindowMs reads wrong buffer when paused

void WaveformWidget::setZoomWindowMs(int windowMs)
{
    ...
    if (m_paused) {
        const RingBuffer& buffer = activeBuffer(); // uses m_transmitting, not m_pausedTransmitting

activeBuffer() returns based on current m_transmitting, but when paused the samples should come from the buffer that was active at pause time (m_pausedTransmitting). If the user pauses during TX then TX ends, changing the zoom window would re-snapshot from the (empty/different) RX buffer. This method isn't wired to the UI yet so it's not user-facing today, but worth fixing now to avoid a subtle bug when it gets connected.

3. kPi vs std::numbers::pi

Minor: since the project targets C++20, you can use std::numbers::pi from <numbers> instead of defining kPi. Not a blocker.

4. clearActiveRing removed — no way to clear samples

Double-click now toggles the settings drawer, which is good UX, but the ability to clear the waveform buffer was removed entirely (the clearActiveRing method is deleted and clear() is now only called internally). Consider adding a "Clear" action to the waveform's context menu, similar to what was just done for the CW decode window in #2115/#2116.

What looks good

• Correctly uses AppSettings (not QSettings) with .save() — consistent with the rest of the codebase
• QSignalBlocker RAII for blocking signals during init — clean
• GuardedComboBox/GuardedSlider for the drawer controls — respects the scroll-lock pattern
• Sanitization on all user-facing inputs (sanitizeWindowMs, sanitizeRefreshRateHz, sanitizeAmplitudeZoom)
• scheduleRepaint correctly derives the throttle interval from m_refreshRateHz
• Settings persistence key naming (WaveApplet_ViewMode etc.) is clear and scoped
• Backward compat: Scope saves as Graph to match the existing deployed value
• Files changed are all within scope

Thanks for the contribution!