So, as you all probably know already, legacy animations are now gone.
There is already a canny post about it to still keep them but it only talk about japanese people discovering a way to use relative paths.
I'll give you one example of what the system will remove and it's something that a lot of people used.
Refer to this album : https://imgur.com/a/XWzPKZ7
tl;dr : The legacy animation animation was used with a fixed joint to lock an object to world position, the legacy animation was set to loop and used to reset the position of the object to your when it's not active, without that animtion, the world object will just move further and further away from you.
every creation using a system like this will basically not be possible.
if you have any easy solution for this system, please feel free to suggest it.
Edit : after some more research, Snail's inventory system is also using legacy animations : https://github.com/theepicsnail/Inventory (Snail is more know for his markers in vrchat). Meaning that this toggle inventory system will also have to go.