They are in my rail planner app, until 23 April. The same in the DB planner. That suggests that they haven't sent any timetables yet for the rest of the year.

If you don't even see these trains until 23 April, then please update your app.

Please note you should not use the rail planner app for planning because it is not reliable and often out of date. It's better to use national planners or apps and for international planning, the Deutsche Bahn website or DB Navigator app is a good choice.

Thanks for your answer and warning about using Rail Planner App. But strange, my Rail Planner app is  updated (Iphone). And yes, DB seems very reliable

You better use sj.se , which also is the best place to make the reservations. Domestic Swedish travels are bookable until the 28th of May. However not all departures are open for reservations as there are uncertainty around construction works. Some departures will not be bookable until maybe a week before. 

Below are instructions for how to make reservations at sj.se

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105/index2.html?postid=20744#post20744