Looking for shortcut keys for trimming and extending layer on short keyboard (no square bracket key)

I'm looking for shortcut keys to trim and extend a layer. I'm using a short Mac keyboard (no square bracket keys). I can use the⌥( and ⌥ )  to type an open or closed square bracket, but it doesn't work as a shortcut in After Effects since the short cut is ⌥[ and ⌥]