Duplicate finder in native app

### Describe the feature you'd like to request

It's hard to find duplicates manually

### Describe the solution you'd like

A filter to find duplicates

### Describe alternatives you've considered

-

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requested by @Don1250

The issue names only the native app and a duplicate-finding filter; no file, test, or entry point is provided. Start by locating the native app's bookmark filtering or search entry point and clarify how duplicates should be identified. Done should be a usable filter that reliably exposes duplicate bookmarks.

Written by the indexing model from the issue text.