Hi @kornelius . I don’t think this is an out-of-the-box feature, but there’s a hack here from a couple of years ago: 

I love that hack! @kornelius if you have any issues loading the chart example, here’s a version of how it’s done: https://analytics.amplitude.com/demo/chart/fhj84m2g

You can see how the formula is referencing a random event (in this case Any Event) multiplied by zero, then adding the specific “target” value to mock this static horizontal line use case.

Thank you both. Seems like quite a workaround, but better than nothing ;)