Addon panel can be reopened by dragging an invisible handle at the viewport edge — please add a visible affordance

[deandre]

Is your feature request related to a problem? Please describe.

When the addon panel is collapsed, it can be reopened by dragging inward from the viewport edge. There's no visible handle at that edge, so the drag target is invisible until the cursor happens to land on it and changes shape. People who keep the panel closed grab it by accident when they reach for something near the window edge.

One user kept hitting this several times a day:

The Storybook addon panel can be opened by dragging an invisible drag handle from the viewport edge and it is absolutely infuriating. I grab the drawer instead of the viewport edge multiple times per day (the cursor changes slightly right before it happens). The drawer should have an explicit visible grabber

Reported on Storybook 10.3.5, though the behavior looks like it predates that version. The sidebar behaves the same way, and it gets worse when Storybook is embedded in another app: Storybook's edge resize handle sits right next to the host container's own resize handle, so trying to resize the outer preview grabs the Storybook sidebar instead.

Describe the solution you'd like

Give the collapsed state an explicit, visible affordance instead of relying on an invisible edge drag target. A small visible grabber shown when a panel or sidebar is collapsed would make it clear where to drag, and would stop the accidental grabs that happen when the drag target overlaps the window edge.

Describe alternatives you've considered

• Don't allow reopening by dragging from a zero-width edge at all, and rely on the existing "show addon panel" / toggle buttons.
• Reserve a few pixels of padding so Storybook's handles sit inside its own UI and never overlap a host container's handles.
• When Storybook is embedded, disable the edge resize handles (or the drag-to-zero behavior).
• Current workaround: use the "show addon panel" toggle button rather than the edge drag.

Are you able to assist to bring the feature to reality?

no

Additional context

The drag-to-reopen behavior appears intentional: you can drag a panel down to fully hide it, so dragging from the edge brings it back. The problem isn't the capability, it's that the collapsed state gives no visible cue for where that drag target is, and the target sits exactly where people aim for other things (the window edge, or an embedding app's resize handles).

Recent accessibility work (#33980, following #33979) made the resize handles keyboard-accessible and visible on focus. That helps keyboard users, but it doesn't add a persistent visible affordance for the collapsed / zero-width state, which is where the accidental mouse grabs happen.

[Sidnioulz]

Thanks @deandre! I agree with you that making the resize handle smaller would help.

I think we could keep the existing hover detection on the entire length of the window to show the handle, but then process drag events only on that handle. WDYT @MichaelArestad?