Block Selection using Option-Drag

In various places in macOS, one can hold down the Option key and drag across a rectangular block of text to make a block text selection similar to how CTRL+V works in Vim to create a Visual Block. You may try this in Terminal or Sublime Text on your Mac to verify.

In Textastic, I would like to have the same Option-Drag feature to create Visual Blocks. It’s a super useful feature to have in a code editor. I apologise if this has already been implemented with some other key combination. If it is the latter, please let me know what that key combination is. Thank you.