you can use https://crontab.cronhub.io/ to generate the corn expression. whenever you need to the schedule other than the one which are listed in the ‘execution frequency’ drop down list then always use debug to update the expression and never save it from schedule task UI as it will override to the one which is selected. in this case UI looks wired as you won’t be able to see actual frequency which is set, just to avoid the confusion, it would be good to something in description which can give an idea what frequency it set and again this would just an indicator.