The select tool palette that you're showing in your screenshot cannot have an accelerator set because it requires user interaction to complete.
Here is the documentation https://pro.arcgis.com/en/pro-app/latest/get-started/customize-the-ribbon.htm#ESRI_SECTION1_0B9AD340...
Thanks for your reply. I just want to quickly select another ferture which needed to be changed when I have too many features. This is available in ArcMap.
If i use mouse to click the "select tool" and then to select the feature, it really waste time.