There are no buttons with actions available straight out of the box in Qlik Sense. To solve your problem you'll probably need to find (or create your own) an extension.
I believe that swr open source project could fit your needs.
Scroll down to the the part about Actions you'll see it supports two action for each button.
You will have to go with an extension to achieve this. I have built an extension : GitHub - reddys10/Input-box-which-updates-a-variable-in-QlikSense
You can use this extension or replicate this functionality in a different one.
download qsvariable from Qlikbranch Site
using qsvariable create a variable
named it vChoice
Add Button 1
label = Top 5
value = 1
Add Button 2
label 'Top 6-15'
value = 2
I understand you have already 2 variables for mesure Top 5 and Mesure Top 6-15, called it for example vTop5 and vTopOther
then in your Bar chart or table add this mesure
hope it helps