Which keybindings should I configure in IntelliJ Cursive to get the "expand" and "shrink" selection behaviour documented in the ParEdit user guide?
The user guide mentions Alt+Up and Alt+Down, but as someone new to structural editing, I'm struggling to find the right keybinding.
It depends which platform you're on. Generally you don't have to configure these actions since they're built in to IntelliJ, they're not Cursive specific. Alt-Up and Alt-Down are for the Mac OSX 10.5+ keymap, recommended if you're on a Mac. In the Default keymap, which is what you'll get if you're on Windows or Linux it's Ctrl-W and Shift-Ctrl-W.
These actions are called "Extend/Shrink Selection" on v14, and on earlier versions (probably for historical reasons) they're "Select/Unselect Word at Caret". They can be found by searching in the Keymaps panel.