Time to SLA add-on has several custom fields which you can export in issue navigator. However, Time to SLA fields have many valuable data other than what you see in issue navigator. You can use SLA Dates Custom Field to grab these separate data, sort them in issue navigator, and export to Excel.
On the other hand, Better Excel Plugin for JIRA is tightly integrated with Time to SLA, allowing you to export all Time to SLA custom fields to Excel in customizable format.
Using the Excel features on Time to SLA data, you can easily create powerful SLA reports.
You can export the Time to SLA specific custom field types like Time to SLA, Overdue Status, SLA Indicator, SLA Overview, TTS - Time String and TTS - SLA Dates to Excel. Better Excel Plugin will automatically recognize the Time to SLA managed fields and export them accordingly.
You can find more info about Better Excel Plugin for JIRA and Time to SLA integration here.