@kisvegabor As you said here:
That logic hasn’t changed in v7. LVGL just redraws every dirty area. However, it seems in v6 the chart is still running in the background while you scroll, but in v7 it stops. So v7 might be slower here.
Anyway, how you implemented this chart? Maybe there is something to optimize there.
No need to say how good it is to optimize more. So with regarding this, I hope this new solution I found to solve my problem will not have any bad effect on your decision in optimizing 
Anyway, here it is:
Based on @kisvegabor 's answer in the issue I opened recently I found that it’s not a bad idea to create an lvgl task for updating GUI parameters and chart.
So I added these 2 lines:
lv_task_create(lvgl_task_refresh_params_callback, 1000, LV_TASK_PRIO_MID, NULL);
lv_task_create(lvgl_task_refresh_chart_callback, 8, LV_TASK_PRIO_HIGH, NULL);
and the result was so satisfying for me.
PS: I call lv_task_handler every 10 ms, Is it O.K to have set the period in lv_task_create less than this time?