So you want to run 3 days one week, and 4 the next, always with 1 day of rest? No problem.
Just go to your Training Settings, click ‘Update’ and set your ‘Target runs per week’ to 4 (or higher) and the ‘Max run streak’ field to 1. Save and let your new plan build.
(You may need to click on the ‘Advanced options’ link to reveal the ‘Max run streak’ field.)