In/Out marks on Timeline

There's nothing wrong with that! Preview Range already lets us loop part of the Timeline, but it’s easy to forget what the original Start/End were after toggling it on and off, especially in long shots or shared files.

In/Out marks would act as a separate, temporary playback range, so we can loop sections freely while the scene’s Start/End stay untouched and never get “lost.”

Not sure I follow. You want to see the Preview Range as some sort of marks, even while it Preview Range is disabled?

No, it's not visualizing Preview Range marks at all.

In/Out marks are separate, always-visible handles directly on the Timeline ruler—like Premiere Pro's In/Out points that you drag or set with shortcuts (e.g., I for In at playhead, O for Out). Hit "Play In–Out" and it loops only between them, every single time, without touching anything else.

Preview Range stays unchanged (still toggle/clock icon for advanced workflows). Scene Start/End never moves.

Why bother? No more "is Preview Range on or off?" confusion—your original frame range is safe, and looping a beat (lip sync, walk cycle) is one click instead of menu-diving.

for quickly setting a preview range, just press P and drag up the range you want to preview. If that isn't what you are after you need to explain your first sentence in more depth.

Right now we keep changing Start/End or toggling Preview Range just to loop small sections of a shot, which gets messy on longer animations

Why? What is messy about it? I have a feeling you are asking for a better preview range user experience by proposing another preview range.

P-drag ( P ) is awesome for quick viewport preview range, but it doesn't fix the state confusion that makes workflows messy on long shots.

The messiness in one scenario:

1. 600-frame shot. You P -drag frames 210-220 to polish lip sync → Spacebar loops it.
2. Jump to frame 245 for foot contact → Spacebar surprise —plays full 1-600 because Preview toggled off (or you forgot).
3. Repeat 10x per shot. Constant "wait, is Preview on?" + hunting stopwatch icon. Shared files? Collaborator renders full timeline by accident.

In/Out marks = zero-state Timeline looping (like Premiere I / O points):

• Drag handles always live on Timeline ruler—no toggle.
• I at playhead → In mark. O → Out mark. "Play In–Out" loops only that, every time.
• P /Preview unchanged for viewport renders. Start/End safe.

It's not "better Preview"—it's dedicated, discoverable Timeline muscle memory so you never second-guess playback range mid-animation.

Jump to frame 245 for foot contact → Spacebar surprise —plays full 1-600 because Preview toggled off (or you forgot).

How can that surprise you when anything outside the preview range is tinted orange. Why would you even look for the stopwatch icon for that.

Having handles in the playback area to drag the scene and preview range would make sense though.

I at playhead → In mark. O → Out mark. "Play In–Out" loops only that, every time.

This already exists for the preview range. Ctrl+Home and Ctr+End are the hotkeys. I admit not quite as convenient as [ and ] but those are already taken for something else. You can always modify your hotkeys though.