What the extension actually does
Save the current tab. Brain Bar is ⌘⇧K / Ctrl+Shift+K. Save the window as a Focus Session with ⌥⇧S. Chrome will ask for the bookmarks permission only if you import from the popup.
The library lives in your Markwise account, not only in the Chrome profile, so Edge/Brave/Opera installs of the same extension — and the iOS app — see the same saves.
Import the bookmarks you already have
Chrome → Bookmarks manager → Export bookmarks. That Netscape HTML file is the whole inheritance. Inspect it with the free analyzer (nothing is uploaded), then Pro bulk import files it.
Free cap 50, meaning search on Pro
Free keeps 50 bookmarks and text search. Meaning search and Copilot are Pro. A large bookmarks.html will hit the cap: inspect the file first, then Pro bulk import if you want the whole pile searchable by meaning.
When to stay on the bookmark bar
A handful of daily links can stay on the bar. Markwise is for the rest: the pile you cannot search by title. Chrome bookmarks remain free and built-in.