...
Making edit buttons just above cursor allows user to select an editing tool faster. It works especially well if the user is constantly switching editing tools. On the other hand, it may get tedious when the user is only using highlighting, and has to select the highlight tool every time after selecting text, which results in one more click per highlighting action. Making the most recent selected tool last until explicitly cancelled (by right click, for example) may help, but going back to learnability-wise, that the knowledge of 'right click to cancel current active tool' needs to be learned somehow.
...