SOLVED: Not a Brave bug.
In an existing Google Docs document, the toolbar appears when loading the page, but while scrolling down to the second page, the toolbar disappears.
Brave v 1.26.67, macOS Big Sur 11.0.1
No problem on Chrome 91.0.4472.114
Failure with shields up and with shields down.
Suggested chrome solutions don’t work. (e.g. Escape, Command+Shift+F …)
Hey @danorton ! Welcome to the community 
Can you provide screenshots of the issue? Also do you have any extensions installed? If so please disable them to see if the problem continues.
Thank you,
Porridge
SOLVED: Not a Brave bug.
When the tab is zoomed, the toolbar can scroll up and out of view and you have to scroll back to the top of the document to scroll the toolbar back into view. This behavior is the same with Chrome.