You can just type the value in, the limit is only when using the input controls. The editor is pretty good at staying responsive even with a massive table, but your chances of a out of memory crash go up a fair bit once you exceed 10 mil cells. The 1000 x 1000 soft limit is supposed to make it harder for users to do this... So just be careful changing those dials, an out of place zero can crash the tab and ruin your day.
At some point in future I may update how the editor works, if we made the table structure sparse then it be able to cope with tables with dimensions in the trillions. Provided they were mostly empty. Although it would be impossible to serialize it to JSON at that size ( as the JSON array format isn't sparse ). This would be a pretty massive change though, and likely increase the code complexity level quite a bit.
If you need really big arrays then file a feature request, it would be an interesting project to work on but we cannot commit the time for it unless we know it's actually something that needs solving!