其他网站找到的解释:
You have too many "active" commands that wait for user input (e.g. Edit object properties while dialog is open).
It is the depth of the command stack used to store unfinished commands
sequence. To avoid this problem, remember to press the ESC key when you
finish one command and want to use another one.
可以修改nestability limit的最大值:
options-> user preference-> nest limit