If they do not need to be global, what you can do is select them in the object list next to the layout editor (on the left by default, I think), copy, and then paste them into the other layout.
Global would work better for XAudio2, and maybe HashTable. It depends on what you are doing with them, I suppose.
I'm certainly not an expert at this, but in my game project, at least, I am using a global HashTable and global Xaudio2.
These allow them to work on all layouts, to be used in all event sheets on all layouts, though they do not show in the Objects display in other layouts. They will show in the event sheet object pickers and whatnot for other layouts, though.
If they weren't global, they'd be reinitialized on the start of a new layout, I think.
Being global, I did not copy/paste them to my other layouts. Being global, they already exist in all layouts.
(However, for most objects - things which have a sort of "physical presence": which can be moved or placed, having a position, size, etc., such as any onscreen objects, you probably won't want to make them global unless you want them to be placed in exactly the same place on all layouts (maybe a HUD or menu or such))
Also, if you will have game saving/loading:
It looks like I set "No serialize" on my Xaudio2 and HashTable. Either that's what I had to do, or I had a reason behind it. I forget. Maybe I shouldn't have that checked, I do not know.