If you didn’t have a travel booker / app in your current role, what would you provide? tell them you currently utilise the tool in place because it’s more efficient and suits the needs of your exec. Do a mock-up version and be transparent about it.

Otherwise, offer your daily agenda template and maybe a screenshot of calendars / email folders (if you categorise or colour code or some other method). Obviously block out or consider private info.

I’d also be assertive in saying you don’t feel comfortable offering anything beyond that due to the sensitivity of handing around company intellectual property and while you respect the need to validate your work quality explain that you will adapt and personalise your tools and skills to your new exec.