To expand a row in a table, you can only link it to one item. Be it a cell, a text box, image, etc. Having a duplicate of the column on the other side of the table will create fields with different names, so the "copy" of a column won't expand.

Note, the setting to expand a row/group/etc is set on the item itself, not the item you click, which can only have one value. You can see my right clicking the row in your tablix, or the group in the Row Groups Pane, and then select Visibility. You can see that you can tick a box to toggle the display by a report item (not items, so only one).

You may be able to do this with Custom Codes, but I'm afraid I've created any (I've generally found SSRS to provide what i need, and if it doesn't, it's normally a "only if it's easy to implement" situation).

Hope that at least explains why what you are trying to do, doesn't work, sorry i can't give much more.