At present the drain is not showing because it is currently hidden under a 3D element (in this case the bench extrusions)
If the drain symbol is modeled separately in a different family (not nested):
- Option 1: In the project module, go to view tab and start "Show Hidden Lines" >> Click Bench >> then click drain...you will get something similar to the below

- Option 2: open the drain family (depending what type of family is is) change it to a work plane based and load to the project...this way you can place it using "On Face" and drop it on top of the bench

- Option 3: model the bench to show 2 D in plan view this way it will not block visibility of elements underneath
If the drain symbol is modeled in the Sauna Benches family:
- first you need to lock the drain to its position under the bench to ensure it moves with the bench (lock it using a dimension to a reference plane or to a reference plane directly)
- To make it show, you have several option...
- Option 1: hide 3D elements in plan view and use 2D representation instead - u can control visibility of the 3D elements not to show in plan view and use symbolic lines locked to the contour of the elements which will show in plan. this way all becomes 3D and you can see drain 🙂
- Option 2: if you want to keep the 3d elements/extrusions in the plan view, then draw the symbolic lines of the drain on a plane locked to the top of the bench