I found the reason but don't understand.
I added the buttons, yesterday, to the toolbar in the partial CUI. now i see a toolbar with the same name appear also in the main CUI file Acad.cuix.
I added the buttons to that toolbar and it updates.
So, i have, always, to add to the toolbar in the main CUI, and then use the transfer tab?
I must have transferd this toolbar to the main CUI, because i see it there, also, and i don't see toolbars from other partial CUI files, like the EXPRESS, in the main CUI.
In this case, i understand, if i transfered to the main CUI, i have to add to the toolbar in the main CUI, right?
And, if i want that my toolbar will have the same behaviour like other toolbars from partial CUI files, i have to remove it from the main CUI, right?
"So, i have, always, to add to the toolbar in the main CUI, and then use the transfer tab?"
It should not be necessary to transfer anything. You should be able to create a toolbar in your custom CUI with the same name as a toolbar in the ACAD CUI. (Although I would recommend using unique names, just to avoid the potential for confusion.)
I think the part you are missing is to modify your workspace and turn on your new toolbar (and maybe also turn off any toolbars that you don't need or want). It shouldn't be necessary to remove anything from the ACAD CUI.
Are you trying to add buttons to an AutoCad menu? I've experienced problems with that in the past. I find the best results are to create a new menu and place all your desired commands toolbars in your new menu. Some will call me crazy, but I've actually duplicated many of the AutoCad menu's in my own menu's and don't have any "out of the box" menu's loaded. I've had no problems customizing as needed over the years, and upgrading to newer versions has been seamless so far. Good luck.