UI settings don't persist between reloads

[pbakaus]

Bug Description

UI settings such as collapsed panel states should persist across reloads. The following settings need to persist:

• Panel state (collapsed/open)
• Layer panel height
• Selected page (let's attach this as hash to the current URL, like Google Slides)

The following should not persist:

• Selected tab in design panel
• Selected tab in element panel

/cc @samitron7

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Acceptance Criteria

QA Instructions

[spacedmonkey]

Related: WordPress/gutenberg#15105

[miina]

@pbakaus Should the settings persist when the user closes the story and comes back to it later as well, e.g. the next day? Or would that be just for a specific editing session when reloading and when reopening the story again after closing, it should be in the default state?

[pbakaus]

imo the settings should persist across sessions, analogous with almost every other design tool. @samitron7 to confirm (or disagree).

[ezxyz]

Should the settings be put in local storage? I'm assuming its across sessions on the same browser (not on different browsers, computers etc).

[swissspidy]

Yeah that'd be something for localStorage. Depending on the feedback above we could easily switch to sessionStorage if necessary.

Bonus: extensible API that supports both, and potentially even persistent storage (e.g. WordPress user profiles) if we'd ever need that.

[pbakaus]

+1. We can start with localStorage (I wouldn't do sessionStorage for now, as I predict users might want some level of persistence per browser).

[samitron7]

Completely agree to paul's recommendation:

"imo the settings should persist across sessions, analogous with almost every other design tool. @samitron7 to confirm (or disagree)."

[maxyinger]

Persists Following:

• Panel state (collapsed/open)
• Layer panel height

#4601

[maxyinger]

Persisting active page moved to separate ticket & detailed here:
#4605

[csossi]

Verified in QA