how it fixes #2840?

The issue in #2840 (unable to set time format) happens because the previous list implementation triggered a full JSON decode & disk read on every single keystroke.
This heavy operation caused the NSTextField binding to lag or reset mid-typing, effectively rejecting the user's input before they could finish.
By checking cachedList (memory) instead of Store (disk) for the getter, the UI binding remains stable and responsive, allowing the user to type the full format string without interruption. The save() to disk only happens after the change is committed.

it does not, since Store has internal cache, so what you do is basically duplicate the login inside Store. But again, how that fixes #2840?

Hi @exelban, thanks for checking this!

You are completely right that Store caches the raw Data, so we aren't hitting the disk. However, the performance bottleneck here isn't the disk I/O, but the JSON Decoding.
Without cachedList, the list getter calls JSONDecoder().decode(...) every single time it's accessed. Since list is used by numberOfRows and viewFor in the TableView, this forces a full JSON decode operation for every frame/cell render, which causes the specific UI stutter/lag reported in #2840 when typing or scrolling.

My change ensures we decode the JSON only once (on init/set) and serve the ready-to-use object from memory thereafter.

Oh, yeah, I see the problem with json. But still, how it fixes #2840?
Problem there that settings does not appear because the widget is not active, how cache will solve that?