CFHideProblems@leksi.net by Leksiq

Until Leksiq reached a noticeable rating on CodeForces, he devotes all his free time to solving problems from the Problemset. Leksiq solves them one by one in order of increasing Difficulty. Leksiq wants to spend as little time as possible on organizational issues, so it upsets him that not for all problems a solution in his favorite programming language can be sent. Having met a similar task, Leksiq immediately moves on to the next one, and the missed one remains in the table. Since Leksiq does not have a very long memory, he often takes such a task for a new one and again opens the condition and again gets upset not having found his favorite language in the list.
Fortunately, now these troubles are in the past for Leksiq: he has developed an extension for the Firefox browser, which, in the interface of the CodeForces website, allows him to hide unnecessary tasks from the Problemset table, show hidden tasks and stop hiding tasks if he suddenly decides to learn new programming languages for himself . He can also transfer the list of hidden tasks between his numerous computers, which, as they know, are in his every room.
Since Leksiq is happy to help to like-minded people, he suggests installing this extension to everyone it can be useful!