Vectorworks has a maximum number of undos. The number is set in Vectorworks Preferences.
The default option is 20 undos. This can include view changes or not, you can choose.
The maximum number of undos that you can set is 100. Be careful though. In the past, a large number of undos has been responsible for crashing due to the heavy memory requirements of so many undos.
I leave the maximum number of undos at 20. It is the default number, and it gives me enough for small changes and mistakes.
Instead of using a large number of undos, I use save and Revert to Saved.
I save the file before I want to carry out a lot of changes. Then I can restore back to this saved version if I want to undo all the changes. You could think of this trick as an Undo to Last Save command (I used to use Microstation, which had an Undo to Mark command).