Normally tinkers stations, stencil station, tool station.. all recognize one another and form a sort of multi-block structure as long as there is a crafting station somewhere in the mix. This works as expected with the slab variants. Sadly when I put a chest slab into the empty slab space that block fails to get recognized as part of the multiblock structure.

You can replicate this by placing a tinkers station and tool station next to eachother (either on the top half or bottom half slab, open the crafting station and noting that the tool station is available as a tab that you can easily switch to. Then place any other slab machine above/below the tool station then reopen the crafting station. Note that the tool station tab is now gone.

What would be amazing is if I could place these stations on top of eachother (either adjacent 2 tall, or all in a single stack) and for them to recognize eachother.

As it stands if I want to have a connected tinkers station set I must accept that the other half slab must be left empty, thus canceling out any benefit I get from the slab form.

i think this is mainly due to tinkers being particular of where you place them iirs. i agree that in this case the "multiblock" should still count. was coming here in fact to see if this very thing had been reported