I have created a profile but it isn’t appearing under the slab edge list?
The profile is now available in the file however you now need to create a ‘slab edge’ family within the file, you will then be able to select a profile for it to use. This can be done in the project browser under families, slab edge.
When creating 2 perpendicular walls (in plan) made of concrete they automatically join. How do I prevent this to show an expansion gap?
If you don’t want the walls to auto connect you can duplicate the material (conc) and revise the name slightly (conc1), assign the new material to just one of them, this will stop them joining. If you want to add an expansion joined to a continuous wall then use the split with gap tool.