Using !include in lovelace dashboard storage mode?

[CentralCommand (Mike)]

No, it’s not possible. If you want more info on why, its in the discussion here:

WTH why not use !include in the raw-editor of the dashboards

Currently it’s still not possible to include files into the raw-editor of a GUI controlled dashboard. This feature will allow the less yaml-oriented users to build better dashboards (e.g. with help of HACS-integrations) without building their full dashboard in YAML.