To put “a variable in a variable”, access the wiki link above and scroll down to “dynamic access”.
But you’ll need to use a variable structure as shown above, and not use it on the main parent of the structure.
So each ‘mark’ object has a object variable. (stage number)
mark11 ~ object.Variable=11
mark12 ~ object.Variable=12
mark13 ~ object.Variable=13
etc.
And I replaced the index number in global variable with object variables.
Also all the objects (mark11, mark12, mark13 etc.) are in the object group ‘mark’