Hi!
There is the same problem here. Launcher settings will not be saved if you modify the Java code for RAM as well as immediately forget the world of recordings even if it is created successfully and saved automatically.
I recommend that you keep your old Launcher running until the latest Launcher update version is available and fixed. Several issues are currently in the latest version of Launcher.
Launcher settings are now saved from TMP after changing the JSON, but within the game has not yet been resolved. In practice, the game saves the world, but when you jump out of it, it reportedly does not find the world saved in the directory, but asks you to create a new one for the first time as before. The game has once been completely reformatted, but it didn’t help.