Improve filtering of output webpage

[jfrost-mo]

What problem does your feature request solve?

I can to use an external script to get the same lead time of the same variable for different cases. It would be nice if this level of slicing was available within the GUI.

Describe the solution you'd like

More slicing!

Describe alternatives you've considered

Do we need a proper SQL database to back it?

[jfrost-mo]

The infrastructure is added in #1713, though information on lead times, etc. still needs to be exposed.