I haven't qliview installed on this computer, however, each object has in its properties the visibility property (Always/conditional) in the general tab.
Let's suppose we call the variable var1 so create it: LET var1=0;
In the visibility of the object write var1=1; (means that if var1 is 1 the object is visible otherwise it is hidden)
In the button go to triggers, external, set variable:
write in the upper box var1 and in the lower box: if(var1=1,0,1)
Now if you press the button the object appears and disappears.
Hope it helps
