Reddit's native saved tab is scroll-only and unsearchable past a few hundred items. Keep syncs your saves via a private RSS feed and makes the whole archive full-text searchable.
Reddit syncing runs through an RSS subscription and requires a paid plan for full-content saves.
Enable private RSS feeds
Go to old Reddit preferences and toggle "enable private RSS feeds" on. The new Reddit UI does not expose this setting, so you need the old site to flip it.
Copy your saved feed URL
Open the old Reddit feeds page and copy the URL next to "saved". It looks like this:
https://old.reddit.com/user/<username>/saved.rss?feed=<token>&user=<username>
Treat this URL like a password. Anyone who has it can read your saved posts. If you ever paste it somewhere by mistake, go back to the feeds page and reset the token to invalidate the old URL.
Add it to Keep
Open settings -> subscriptions, add a new web feed, and paste the URL. Keep checks the feed every few hours and saves new items into your library as you save them on Reddit.
Limits
Reddit's saved feed returns your recent saves, not your full history. Older items that are no longer in the feed will not backfill automatically. A one-time historical backfill is on the roadmap.
If you reset your feed token on Reddit, the old URL stops working and Keep will start showing a sync error on the subscription. Copy the new URL from the feeds page and update the subscription to start syncing again.