Shift+Drag to resize all track heights at the same time is broken in Premiere 26.2 and 26.5 Beta

Issue: Holding the Shift key while dragging track dividers in the timeline header fails to adjust all track heights simultaneously. Instead, Premiere completely ignores the Shift modifier key and only resizes the single hovered track.

Steps to Reproduce:

1. Open any sequence containing multiple audio or video tracks in the timeline panel.

2. Hover the mouse cursor over a track divider within the track header zone (next to track names/locks) until the vertical resize arrow cursor appears.

3. Hold down the Shift key on the keyboard.

4. Click and drag vertically to change the track height.

Expected Result: All corresponding video or audio tracks should resize concurrently to match the height of the track being dragged.

Actual Result: Only the single track under the mouse pointer changes height. The Shift modifier is completely ignored.

Screen Recording: https://drive.google.com/file/d/1MXTTV74yZD1vIpy4q9dX3JdMTPH0zwpG/view?usp=sharing

Premiere Version: 26.2 (Release) and 26.5 (Beta)

Operating System: macOS Tahoe 26.5

GPU Driver (Windows only): N/A (Mac System)

Video Format: N/A (UI / Timeline bug, not clip or codec specific)

Helpful Context

• Does it affect all projects or only some? It affects all projects, across the board.

• Does it affect new, empty projects? Yes. Creating a brand new, empty project and sequence yields the exact same broken behavior.

• When did the problem first begin? The problem began immediately after updating the operating system to macOS Tahoe 26.5 and running Premiere version 26.2 and above.

Additional Note for Engineering: I am running a MacBook Pro 16-Inch (Nov 2023) with an Apple M3 Max and 64 GB of unified memory. I have already attempted a full Premiere preference reset, deleted the cached Layouts directory, and toggled OS Accessibility settings for Premiere off and on to rule out OS background permission blocking. The issue persists globally.