This may not help a lot, but I'm going to share some ways to deal with the new change of brilliant.
1.About the problems you previously liked, you can go to the community page and choose "Following" for popularity. You may find some of the problems you previously liked, and also finds the problems you posted a solution or comment on it.(View Maria Kozlowska's idea, it is much better.)
2.If you want to find a certain topic, you can type in the website "https://brilliant.org/tags/topic/".
For example, if you want to find something about divisors, you can go to "https://brilliant.org/tags/divisors/"
3.If you want to find a certain problem (you have to remember the problem title), you can also type the website "https://brilliant.org/problems/title/".
For the title, put "-" for spaces, and neglect all the other punctuations.
For example, if you want to find "The 100(th) Problem", the website is "https://brilliant.org/problems/the-100th-problem/"
4.If you want to find a note, you can type the website "https://brilliant.org/discussions/thread/note title"
(For 3 and 4, if a problem or note title have been changed, then it'll be harder to find them because the website wouldn't change.)
5.If you really want to find a member, you can look for a problem you got right, press "post a new solution", and mention someone(@name). Don't post it yet, when you preview it, you can get to that person's profile by clicking the connection. (And delete the solution after you find that person)
Other member's ideas:
1.You can access a list of liked problems by typing an address: https://brilliant.org/profile/your-brilliant-user-name/favorites/
Use the user name that appears in your profile url. -by Maria Kozlowska
For example: The website of my previous like page is https://brilliant.org/profile/x-id8l3p/favorites/. About the "x-id8l3p", you can go to your profile and see the website.
Also, you can find the members you followed by typing the website: https://brilliant.org/profile/your-brilliant-user-name/following/; or find your previous followers: https://brilliant.org/profile/your-brilliant-user-name/followers/
2.Search on Google. -by Michael Mendrin
If you have any new ideas, comment under!