The menu entry to save a custom orientation is in the View menu on the bottom of the 3d view. The new orientation then appears in the orientation rollout of the bottom bar. But I also don´t know how to copy an orientation like they did in the video you posted unfortunately.
This error that you show here happens also in Blender, and at nearly every menu item. It’s a development feature so that you can edit the translations. This requires to have everything set up in the right way. And obviously something is missing. But i have no idea what. I have never tried to modify the translation. And Bforartists doesn’t have translations anyways. At least for now. Even when the language packs are onboard
Davis pointed already at it. We have moved the menu item to the view menu. But it seems that you stumbled across a bug here. We have the edit box in the properties sidebar removed. And this means you cannot remove the new created orientations anymore.
I will make an issue, and reimplement this dropdown box in the properties sidebar.