Allow Value Guides on Charts to be variable, based on field values

[TaraHaynes]

I am working with data that has variable conservation targets based on the area of the landbase - eg. we need to conserve 10% of the total unit area.

Currently, value guides only allow a static number to be input:

I would like to be able to at least input value from a field, eg.: Value = {Protection_Target}

Having the ability to use Expressions/Arcade here would also be fantastic!

Currently, the only workaround I have found is to create a dot-style target point, but user feedback indicates that having a line on the graph would be preferred:

Preference: