Custom metrics editor "Expert mode"

The custom metric editor now lets you edit the metric definition by typing. To do this, active "Expert mode" by hitting the </> symbol in the metric definition area:

This is particularly useful if you need to copy a custom metric or make changes that otherwise would require a lot of clicking, dragging and dropping.

For example, if you have the custom metric "Native conversions" and want to create a "Cost per native conversion", you could use this feature to accomplish this:

In a bit more detail, here's what's going on in the gif above:

1. In expert mode, copy definition of "Native conversions"
2. Create new custom metric
3. In expert mode, paste definition
4. Add "Cost", the division symbol and the parenthesis
5. Save metric