The indicators used can be customized:
- For the prefix key indicator, set `@themepack-prefix-key-on-format`
and `@themepack-prefix-key-off-format` options. The off format must be
the same length as the on format to avoid weird behavior.
- For the pane sync indicator, set `@themepack-pane-sync-on-format` and
`@themepack-pane-sync-off-format` options. The off format must be the
same length as the on format to avoid weird behavior.
