I think we should separate the 2 operations that I want to do. You have 1 sketch on the 2 legs and 1 sketch above the other 2 sketches. For me it would be necessary to stire them so that each leg has its sketches for the extrusion.... a liver the whole thing sindé you have to make a 3d sketch that reads the sketches and there it works... see PJ
The 3d sketch is to give direction. You will have to repeat the operation once again for the other branch and then I think you will want to symmetrical the whole thing.
I'm sending you the STEP as well as the part in 2016 because it seems to me that you have it too. And for the STEP you can use Featureworks which will recognize the functions in the room... Before I had a bug because it didn't work without the 3d sketch and now I do.... Not to understand anything...
You opened the STEP and the room with 2016??? For gt22, in fact it's a part with 4 branches and on 2 of them he had the common sketches. The bottom sketch on each of the branches and the top sketch ditto. That's why I told him that he had to delete one for it to work. ..