There are three kinds of task, and the difference is where you type them.
My tasks is your own list, on the Tasks page. Type things there, drag them into the order you want, click a title to edit it, and tick one to cross it off. Crossed-off tasks sink to the bottom; the last 10 stay there and older ones quietly clear.
Session tasks are the ones you type inside a lobby or room, under the heading This session. There is no limit on how many you line up. The lobby and the room give you the same row: tick one off, click its title to edit it, drag it (or hold it on a phone, or use the Move up / Move down arrows) to change the order, and the order is kept for that session. They show on your recap afterwards, and they never appear on the Tasks page - unless you tap the little list icon on one to keep it in My tasks.
Recurring tasks are a standing list of things you do most sessions. Every room offers them under "Add from My tasks"; adding one puts a copy in that session, so the recurring list itself never changes.