I was thinking maybe something like this - 1 extra bar with full scale and guiding lines capturing the proportion:
                                10 %
Scale:      0--------|______________________________________________________________________|
                 .               .
                 .               . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
                ↓                                                                                                                                          ↓
Group A: 0------------------------------------------------________________________________|
Group B: 0--------------------------------------------------------________________________|


Or even just a down-open horizontal curly bracket ("top curly bracket") above the charts:

                                                        10 %
                                                       &#9182; <---HTML code of the top curly bracket symbol
Group A: 0------------------------------------------------________________________________|
Group B: 0--------------------------------------------------------________________________|

Hi, some feedback on the visual side of the figures:
The scaling feels really strange when a value 6-7 % shows as a ~70% piece of the total, especially given that later on, a value of 32 % is shown as ~85% piece of the total.

Only the last graph seems to actually be scaled to 100 % at the total.

I think the first two would be clearer with a full-scale reference bar and "zoom-in" indication that the following ones display a smaller percentage as their total.
And I'd say the third one has big enough values to scale to 100 %.