The relation to Squeezer is that both of these can be useful when you've had a large amount of output written in the IDLE shell. I prefer Squeezer as a solution for this issue, for two reasons:

1. Squeezer catches long outputs before they are ever written in the Text widget, so the performance degradation doesn't happen at all. This also means that for truly huge outputs, Squeezer will still work, while otherwise IDLE may become completely stuck before a user would have a chance to clear the shell history.

2. Squeezer gives the user access to "squeezed" text in several ways: copy to the clipboard, open in an external viewer or expand into the shell. Otherwise the user must choose between a shell with some useless output hiding the useful history, or erasing the entire history.

Still, I still think clearing the history could be a useful feature, though. This is a common feature in terminals and it has been requested relatively often.

Note that making ClearWindow and Squeezer play together nicely is non-trivial. I'm likely going to have ClearWindow include special support for Squeezer.