Making static configuration variable backed is a very common class of feature request we see. It’s not trivial to automatically enable this everywhere - as variables can have async loading states that need to be handled in the UI of each widget. We track each of these requests individually internally.
For charts specifically you will have much more flexibility with the Vega chart widget, and possibly a function backed Vega chart config. As @arjunsoni mentions, a function backed X/Y chart layer similarly offers additional flexibility.
Please open a new thread with a specific variable backed config request in the future for anyone who encounters this thread!