This little extension will add an 'All' button to the In/Out Box. So you can select all displayed items with one tap. The most other builtin application have such a function, for the In/Out Box it was probably forgotten.
Please make a backup first. It's always a good idea to backup your device before you install a new program. Even if we have tested all of our programs very intense, because of the variety of existing programs and system configurations no one can guarantee that no problem will occur.
Transfer the IOSelect.pkg to your Newton OS device by using an appropriate package installation program, like NBU, NCU or the Newton Package Installer.
The only user interface of IOSelect is the additional 'All' button in the In/Out Box. Tapping on it will select all items in the selected folder. Tap again on it to deselect all.
If you have installed a lot of applications adding buttons to the In/Out Box, it is possible that you can't see all of them.