Periodic invoices cannot be created from the mobile; only management is available.
To access periodic invoices, select the documents tab and press the card at the top of the screen.
In the list of your periodic invoices, you'll find
document status (in progress, completed or scheduled)
billing mode (automatic or manual)
date of next invoice
Click on an invoice to access the available actions
The generate button at the top of the screen will generate periodic invoices whose due dates have not yet been set.