## Summary of the Pull Request
In the wake of #6635, a couple things got missed in merges:
* `toggleRetroEffect` didn't get into the schema, nor did `renameTab` or
`commandPalette`.
* `toggleRetroEffect` also didn't get a name
Furthermore, I thought it might be a good idea to start sticking
commands into `bindings` even without `keys`. So I tried doing that for
`opentabColorPicker` and `toggleRetroEffect`, and found immediately that
the labels for the key chord still appear even when the text is empty.
So I added some XAML magic to hide those when the text is empty.
## References
* #6762
* #6691
* #6557
* #6635
## PR Checklist
* [x] Closes#6762
* [x] I work here
* [x] Tests added/passed
* [n/a] Requires documentation to be updated
## Detailed Description of the Pull Request / Additional comments
* See also: https://docs.microsoft.com/en-us/windows/uwp/data-binding/data-binding-quickstart#formatting-or-converting-data-values-for-display
- make sure to switch to C++/WinRT at the top!
## Validation Steps Performed
Removed all my manual actions, ran the Terminal:
5bc31a1e16
