The persons who have a training question on the waiting list can easily be contacted via a mailing.
Menu - Module(s) - Mailing - New - select data group 'training question' and choose a desired template. Click on 'save'.
On the tab 'Recipients' of the mailing you can select the desired persons/training questions and add them to the mailing. Set the status of the training question under training question criteria to 'waiting list'. For example, it is also possible to filter by company/training/period/etc.