Hello. Question more to the forum administration. I've not been here for a long time and perhaps forgot how everything works here 
. Going to the "Watchlist" section, I saw that none of the topics that I subscribed to are on the list. When I going to the "Edit watchlist" section, everything are in place (can select and delete them). Topics in the "Watchlist" appear only when there are new messages in them, or this is a bug and topics should always be visible?
From your account's watchlist page, you will see four options, the following twos like match with your question.. Going to the "Watchlist" section, I saw that none of the topics that I subscribed to are on the list. When I going to the "Edit watchlist" section, everything are in place (can select and delete them). Topics in the "Watchlist" appear only when there are new messages in them, or this is a bug and topics should always be visible?Watch list posts
- This will add all topics you've posted in to your watchlist.
Watch list notifications
- This will add all topics that you're receiving notifications for to your watchlist.
You can customize how you receive notifications in your profile page
- Turn notification on when you post or reply to a topic.
- When sending notification of a reply to a topic, send the post in the email (but please don't reply to these emails.)
Current topic notifications
For topics and boards I've requested notification on, notify me of:
- Replies and moderation
- Moderation only if I started the topic
- Only replies
- Nothing at all