Can I set a default billable status for expenses?

Yes, you can set a default billable status for expenses.

1. Click on Setup under Preferences in the Sidebar.
2. Click on Expense Preferences and scroll down to Bill Projects for Expense.
3. You will see two options:

Billable - This will make new expenses billable by default. 

Non-Billable - This will make new expenses Non-Billable by default.