Any way to conditionally SHOW a block ONLY when (all) other blocks are HIDDEN?

Dear community,

I have a website with a menucard split into 4 categories. These categories are 4 separate list-blocks (the titles of these list-blocks mention the categories). Instead of each block showing an ‘empty’-message, a much better user experience would be to trigger a block (with a button to continue, instead of just a message) ONLY when ALL other blocks are empty (and hidden).
Maybe someone can help me with a custom code to trigger BLOCK3 when BLOCK1+BLOCK2 are empty?