If you have updated your Galaxy Note 9 to the Android 10 with One UI 2.0 and even after the latest Jan update, if you think that UI responsiveness is not as good as it was in Android 9 with One UI 1.5 then here is the solution to it.
Well there is one solution always is to reset the device and start configuring the device once again but that is very time consuming process and there is no guarantee that even after the complete factory reset the Note 9 will be as smooth as it was with Android 9.
Received the new Feb 2020 security update for the Note 9 and I have observed bit better transition performance in One UI 2 animations. But still not as smooth as it was in Android 9. I will still recommend to use the following guide to make the phone UI speedier.
After doing lot of observations, I had come to conclusion that this is not actually poor optimisation of the code in Android10 Samsung has used but rather not fully optimised transition animation scale and its performance for the Note 9 with its Exynos 9810. To optimise this there is very simple solution right now. Follow the steps below.
Click on settings and head to about phone, click on software info, click multiple times on Build No so you will get the option for the Developer mode.
Open Developer mode by again clicking on settings and scroll down to the bottom.
Once the Dev mode is open, scroll down and find Category - Drawing, just below the Category named Input.
There you will find Transition Animation Scale which will have default value as 1X. Just change this value by selecting the 0.5X and keep all other animation values to 1X only.
Now exit the developer mode and boom. You will immediately notice more fluidity in opening/closing of apps animations and also feel that UI speed has been boosted.
You can also try this in Galaxy S9+ since that also uses the Exynos 9810.