How can I prevent unsaved changes from disappearing when I switch between tabs?

Use Page Composer to configure field settings so that edits are automatically saved.

To do this, edit the task flow using Page Composer. In a sandbox that includes the Page Composer tool, open the page where the field appears. Click Tools > Page Composer to enable the Page Composer view, and then click the Structure tab. Select the field component, open its properties panel and select the Auto Submit checkbox.