Test: Settings editor splitview

[rzhao271]

Refs: #79581

• macOS @alexdima
• linux @aeschli
• windows @stevencl

Complexity: 2

Create Issue

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1. Open the Settings editor
2. It has a splitview now!

• The sash width should be retained upon reloads.
• The min and max widths of the table of contents should provide enough variation for the user, assuming the window is wide enough. If the window is too narrow, either the user would not be able to resize the sash much, or the table of contents will hide itself.
• The behaviour of the splitview should make sense when the user resizes or maximizes/minimizes the window or other parts of the editor.