Change undo history limit

Unfortunately There is no way to change the undo history limit via the preferences menu, but there is a way - using the Registry. Press [Ctrl or Command]-[Alt]-[Shift]-[/] and select “Registry”.

Scroll down to "undo.documentUndoLimit" and change the value to whichever you want (note that it can, or it will, consume more memory if you increase this number).