In OpenBuildings Designer Update 9, after clicking on the ‘Slab’ toolbar from the ‘Architectural’ or ‘Structural’ ribbon only the ‘Place Compound Slab’ dialog appears. From there the old legacy slab can not be placed.
To solve this issue there is a Key-in that can bring back the old legacy slabs in OBD.
The required Key-in is,TFPLACE FORM 1SLABNEWDGYou have to put this key-in in the ‘Key-in’ dialog box.After that, you can get the old ‘Place Slab’ dialog from where the old slabs can be placed. Here is a video where the solution is demonstrated,