No, that star button is fixed in the page actions container and you can't hide/remove it like previously was possible via the right-click context menu.

There is no built-in feature to customize that icon, or other icons that appear in that "Page Actions" area of the address bar.

There is an unofficial / unsupported workaround, which is to create a style rule file containing instructions related to the button (a userChrome.css file). A great resource for personal help with style rule hacks is this subreddit:

https://www.reddit.com/r/FirefoxCSS/

I also have general background on my website:

https://www.userchrome.org/

Note that hiding the star via CSS can cause issues because it can no longer be used as an anchor for the edit this bookmark dialog.