We should have themes for avast secure browser, I’m bored of the white theme and it needs a little more color. Anyone else agree with me? 
The whole point of the Avast Secure Browser (ASB) is that it doesn’t allow lots of different add-ons, etc. to be added to the ASB.
I thought there was some talk of a Dark Theme, but I don’t know if that has been actioned.
And they should make it so that people can make custom themes. 
Right back at U
What would be the point of a Secure browser if you allow everyone to make their own changes to the browser.
There is nothing to stop you using a browser that you can make your own modifications. And only use the ASB for secure purposes, banking, etc.
I hope this answers your question.
https://forum.avast.com/index.php?topic=93544.msg1555237#msg1555237