I have a question of feasibility. On the attached file you can see 3 boxes A,B,C. I would like to make a selection of the form A for example so I would like to click on "this one" to see a cross but all this in block mode and without breaking it.
It can be made 3 more boxes under the letters to make the selection.
It must be feasible by using macros. Clicking on this area could, for example, show or hide an "A" layer that contains only a cross superimposed on the block. The same goes for B and C.
Why not also create this cross as a block, put it in your personal bib and all you have to do is insert it by dragging and dropping and make one of the ponits coincide on the right square.