I put down a split top, and try the following, with increasing levels of irritation each time it errors:
@extension=webp
@extension="webp"
`@extension="webp"`
`@extension`="webp"
@extension='webp'
etc.
Eventually I remember there's a labs 'filter by value top', but even that doesn't work unless you remember to set the operation to 'contains', and I realise this is all way harder than it needs to be.
Can the tops expression fields be made more forgiving with text? Especially considering that comes up so often in tops graphs?
Also any kind of help would be appreciated within the UI when constructing tops expressions, and be easy to find in the docs. I always have to search around for too long to get the info I need, in the end its easier and faster to get the Labs team to write a helper top, or to vetch here on the forum.
-matt