I do not have an Android device, and I have never used Brave Sync. Some time ago, I started using GoodSync to run one-way data backups from Windows 7 Pro folders to external hard drives.
GoodSync also offers: ‘https://www.goodsync.com/for-android’
GoodSync for Linux OS: ‘https://www.goodsync.com/for-linux’
"I suspect . . . " that might work for you. Read that [first link’s] page slowly a few times - you’ll get the gist of it. There, I had to read the “Install and Configure” portion a few times.
So, instead of being frustrated by BB (Android) Bookmarks export, you might use GoodSync to get the Bookmarks file from the Android device.
You probably could edit the Bookmarks file. It might be a JSON file.
PS. I wonder if the following steps for exporting Chrome (Android) Bookmarks, might work:
‘https://www.apeaksoft.com/transfer-data/android-export-chrome-bookmarks/’
There, scroll down to:
