In recent versions of Firefox, there's no way to cancel creating a bookmark: the bookmark is created immediately and then the "Page Bookmarked" dialog allows you to move it or remove it.

Some users have noted a problem where that dialog closes prematurely; I don't know whether other threads on that have identified why that sometimes happens.

Over the years, there have been many add-ons created to modify how bookmarking works, so perhaps there's one that works in the older way still?

So how do I stop the dialog box from closing before I have a chance to put the Bookmark into a folder? This is the main reason I use FF, the Bookmarks can be organized into folders easily. Do I need to investigate other browsers? I've spent a very long time trying to fix the "mistakes"!

Hi nhkathy, I don't remember whether the cause of the occasional early closure problem -- quicker than 3 seconds -- was discovered. You can call up the editing panel to select a folder after it closes as a workaround. On Windows, for example, press Ctrl+d. If you would like specific comments on your Firefox, please start a new question and share your system and add-on information.

You can start here, scroll down past suggested articles to continue with the form:

https://support.mozilla.org/questions/new/desktop/fix-problems