Although there’s no explicit option to transfer bookmarks, you can always use one of many workarounds. For instance you can export your bookmarks from another Android browser, then move the HTML file onto your computer and import the bookmarks into the desktop version of Brave. Then, using Brave sync, you can transfer them to the mobile version of the browser.
If there’s no export option on the mobile browser you’re trying to get the bookmarks from then you can use that browser’s sync to transfer them to the desktop version of that browser. For example you can use Chrome sync to move the bookmarks from the mobile Chrome to the desktop one, then import them from desktop Chrome to Brave desktop and sync them to Brave mobile with Brave sync.
It’s a lot messier but it works.