Ok, I discovered a repeatable way of getting it do show the bug. Here's how I can make the original report happen consistently on my iPhone:
- Go to either Tuning Curve or Inharmonicity.
- Rotate device to portrait view (if not already there)
- Rotate device to landscape view
- While in landscape view, click Done to return to main tuning screen
- Custom toolbar items are not visible
If I rotate to portrait and then back to landscape, they will then appear as expected. So, not a big deal, but worth addressing anyway, I think.