There were some changes to the site, which is cool, but I don't understand what I should do about this message that pops up :

Non-Retroactive Changes

Writing Adding
These changes are not retroactive; words already added from My Lists to My Words will not automatically have their writing items added. There are two choices:

Reset My Lists to the beginning, so that you will begin to add any missing writing items to My Words. Items already added to My Words will be unaffected.
Leave My Lists where they are, only adding writing items from now on for the rest of My Lists that are not finished yet.
If the lists are left as they are, you can always manually set them back to the beginning by going to those lists and editing the study settings to your liking.

All I want is for the items that I practice to be added to the SRS review Queue, just like they were in the past, and I want all the stuff that's already in the SRS review queue to stay there. What should I do?

I'm not sure where this message is coming from, but is it something like, in this list you have some items which haven't had some of the parts added? Writing specifically.

If you're happy with stuff that has been added before has all the parts you want, then 'leave my lists where they are' should do it. I guess the 'only adding writing items' from now on must actually mean writing + other selected parts. That sounds like the one you want.

I personally used the export tool and started a new list of the 'not yet added' sections from the old queue. I felt it was neater.

You added 'writing' to the list of parts you are studying. The message there is just saying that you won't necessarily learn the writing for the parts of the lists you have already studied, unless you reset them from the beginning. To make sure you learn all the writings for all the words and characters in all the lists you are studying, you'll need to reset them to the beginning to go through the whole thing. Otherwise, you can simply leave them as they are and only learn the writings for the lists you are studying, going forward. Does that make sense?

@Scott So if I select "reset to the beginning" , am I going to get hundreds of new items in my writing review queue ?

Not immediately. It adds words gradually to your studies as usual, or when you click the green plus button. But writings are the only new things you'll be getting for a while, at least until you catch up on the lists you're studying. If you choose not to reset your lists immediately, then you control when the lists go back to the beginning. But yeah, you have to manage it.