I have a flowline connect to Christmas tree. There are two cases:

Case 1: christmas tree move up from balance point --> D1
Case 2: christmas tree move down from balance point --> D2

There is one spring required to design. I set multiple spring design load cases = 2 and chose "Max travel" design option

With D1>D2, the program selected spring with D1.

I have to check again this spring to ensure D2 also produces hot load within working range and load variation less than 25%. This is extra manual work.

Question: can Caesar II do this automaticaly?

No.
There's too much going on here.
Find the spring that has the balancing load near the middle of the table and make sure you can move up and down to the node deflections associated with D1 & D2.

Will Caesar II be upgraded for this feature in future?

I do not believe this item will be high on the development list.