Opening hidden files
On El Capitan and later, the checkbox “Show hidden files” in the open panel can toggle the visibility of hidden files in the panel.
You can also meke them visible as follows:
- While holding down the Option key, choose File.
- Select Open Hidden.
- If you press the Option key while showing the File menu, Open will turn into Open Hidden.
- Pressing Command-Option-O gives you the same result.