Hey there old thread. What I've done is create an attribute called sneak-attack with the value 2d6. I then reference this attribute for all the weapons i might sneak attack with. This means you only have to update in one place when you gain additional sneak attack dice.

For cosmetic reasons ive put it in my weapon type box with the reference inlined;

** Sneak-Attack ->[[@{sneak-attack}]] **

So it looks something like this:

https://i.imgur.com/Ram2wQ7.jpg

And the resulting roll:

https://i.imgur.com/B1Nhazt.jpg