Controlling Programatically Created Array of Buttons in Another Callback

To begin, I setup my code similar to this example Here

My goal is to create an array of NxM rowsxcols of state buttons. If the row/col of the button exists in a separate list, then the button is given a value of "1" and made green and enabled, where those that just fill in the rest of the array are given a value of "0", made red and disabled. Each button is assigned to a callback that utilizes the src.Text or src.Value to determine what button was pressed. If a button is pressed it changes color from red to green. This all works well.

The problem that I can't seem to overcome is how do I reference individual buttons in other callbacks or throughout the script? A good example would be how to program a "Select All" or "Deselect All" button. Even though each button is assigned to a UniButton(i,j) this lies within the callback function that loads the list and the array and therefore is not accessible outside of that function. Assigning the 'app.' properties yields a 'Unable to perform assignment because dot indexing is not supported for variables of this type.' error. Maybe I am missing something fundamental as I am not a programmer.

Another example of something that would be nice is to be able to pull the current state of all the buttons in the array.

The code is below

        function mybuttonpress(app,src,event)
            src.Value
            src.Text
            if src.BackgroundColor==[0 1 0]
                src.BackgroundColor=[1 0 0];
            else
                src.BackgroundColor=[0 1 0];
            end
        end
        
        function LoadFileButtonPushed(app, event)           
            CellContOne=containers.Map(totalrows,totalrows2);
            allKeys = string(keys(CellContOne));
            
            for i=1:rows
                for j=1:cols
                    UniButton(i,j) = uibutton(app.Panel, 'state');  %Creating a Button
                    UniButton(i,j).Position = A;  %Giving the Button a position
                    UniButton(i,j).Text = totalrows(j,i);
                    UniButton(i,j).BackgroundColor=[1 0 0];
                    
                    if ismember(allKeys(w),app.srscs)
                        UniButton(i,j).BackgroundColor=[0 1 0];
                        UniButton(i,j).Value=1;
                    else
                        UniButton(i,j).Enable=0;
                    end

                    UniButton(i,j).ValueChangedFcn = @app.mybuttonpress;  %Callback function
                    A(1) = A(1) + sizeW; %Position change for the next Button

                    w=w+1;
                end
                A(1)=1;
                A(2) = A(2) - sizeL;
            end
        end
        
        function DeselectAllButtonPushed(app, event)
           ?????
        end