[FEATURE] Custom Aspect Ratio / Export Resolution Options #911

Problem

Currently the editor only exports video in 16:9. This is a big limitation for anyone creating content for mobile-first platforms (TikTok, Reels, Shorts) or square formats (Instagram feed).

Request:
Add an aspect ratio / canvas size selector before or during the editing process, with at least:

16:9 (landscape — current default)
9:16 (vertical/portrait — for Reels, Shorts, TikTok)
1:1 (square — for feed posts)

Why this matters:
Most short-form content today is shot and published vertically or square. Being locked to 16:9 means users have to pre-crop or post-process footage in another tool just to get the right dimensions, which defeats the purpose of using an all-in-one editor.

Suggested implementation:

A dropdown or toggle in the project/export settings for aspect ratio
Canvas/preview updates live to match selected ratio
Source clips auto-fit/crop (with option to reposition manually) into the new canvas
Export respects the selected ratio’s resolution (e.g. 1080x1920 for 9:16, 1080x1080 for 1:1)

Solution

Project setup / export settings panel — add an “Aspect Ratio” dropdown with presets: 16:9, 9:16, 1:1, and optionally 4:5 (Instagram portrait) and Custom.

Canvas behavior — when a ratio is selected:

The preview/edit canvas resizes to match (e.g. 1920×1080, 1080×1920, 1080×1080).
Existing clips auto-fit using a default mode (center-crop or fit-with-blur-bars), with a manual reposition/scale handle so users can adjust framing per clip instead of being stuck with the auto-crop.

Export encoder — pass the selected canvas dimensions into the render/export pipeline instead of hardcoding 1920×1080, so output resolution matches the chosen ratio.

Backward compatibility — default to 16:9 if no ratio is picked, so existing projects/workflows aren’t broken.

Nice-to-have (v2): allow switching aspect ratio mid-project and remembering per-clip crop/position adjustments, so users can repurpose one edit into multiple formats without redoing framing from scratch.

Alternative

**Alternatives

A clear and concise description of any alternative solutions or features you’ve considered.**

Manual post-export cropping in another tool (e.g. CapCut, Premiere, FFmpeg): works, but adds an extra step outside the app and defeats the purpose of using one editor end-to-end.
Fixed preset “export as vertical” button with no live canvas preview: simpler to build, but users can’t see/adjust framing before exporting, so crops often cut off important parts of the shot.
Letterboxing/pillarboxing instead of cropping (keep 16:9 source, add black bars to fit 9:16/1:1): avoids losing any footage, but looks unprofessional for social content and isn’t how most creators want their videos to look.
Auto-crop with AI subject tracking (no manual adjustment): nice long-term goal, but more complex to implement first and doesn’t give users control, so it’s better as a v2 enhancement on top of the manual aspect-ratio selector rather than a replacement for it.

Anything else?

No response