Hello,
I got group elements in repeating group, which are showing when button with dots is clicked. Is there any way to hide those elements from one cell when button with dots are clicked in another cell? I attaching video to show how it looks right now. Group focus is not an answer as they cannot be nested in other groups or RGs.
For your surprise, yes, you can do it using a Group focus inside a reusable elements. 
Take a look here:
Thanks for you help! Indeed, by this way I could add focus group to some element which will be added to RG. Problem is that using this element I cannot access other elements from particular page. For example, I would like to hide some elements when the button from this focus group is clicked.
to reusable element outer part ie like the “Page”
you can add a state
when you click in reusable element you change that state
then on your main page you can add a workflow “do when condition is true”, when reusable element state X is Y then hide group Z.
Problem is that I cannot access from any page any state which are set on the reusable element or reusable page. Could you please tell me something more?
EDIT:
When reusable element is in repeating group I cannot access its states or other elements.
so the state needs to be on your reusable. not in a group in the reusable but reusable itself.
then you can access it from your page this reusable is on
using in this example "header2021s index signup? is yes
As I mention above, it works when reusable is not in repeating group. When its in RG nothing cannot be accessed. 
so if you click button inside your reusable you set state on outer reusable to X
when outer reusable state is X you can use “do when condition is true” to make something else show /hide on your page
Exactly, but when you add reusable element to repeating group cell they become inaccessable.
