Reference

What needs the Source panel or an agent

Most editing has a form in the app: adding and arranging blocks, the chart, scorecard, table, sankey, and control forms, creating params, the whole datasource lifecycle (SQL, run, snapshot, rename, delete), field labels and formats, dashboard duplicate/import/export, and comments.

These things have no form, and you write them in the dashboard's JSON:

• A chart's advanced Vega-Lite: layers, selections, and custom transforms. The chart form covers the mark, the x/y/color/size encodings, aggregate, sort, stacking, and tooltip. For the rest, "Edit spec" in the chart's Properties opens the raw spec.
• Marks and encoding channels that the chart form's menus leave out. The menus hold the common ones. Vega-Lite has more marks, such as tick, rule, text and boxplot, and more channels, such as x2, row and column. The canvas draws whatever the spec asks for. When you select a chart, the Code block beside it names what the form does not edit.
• Field thresholds, value mappings, and row-level calculated columns. A measure's formula has its own editor in the datasource's Fields section.
• A datasource's source, which says where its rows come from. bigquery queries the warehouse. derived runs SQL over the other snapshots, in your browser and on the server. imported is data you uploaded or pasted, so there is nothing to run again. file runs SQL over the bytes of an uploaded file. url runs SQL over a Google Sheet or a file at an address. database runs SQL in a database that the operator of this site registered, as a registered service account. To change a source after you create the datasource, edit it in the Source panel.
• A datasource's runsAs, which says whose credential the run uses. On arkush.app, a BigQuery datasource runs as user: the query runs in the browser of the editor who selects Refresh, under that editor's own Google account, and no schedule runs it. On an org install, the editor shows a Runs as field on a BigQuery datasource when the dashboard is saved on the server and Google lets you use at least one registered service account. There, set runsAs to a service-account email that Google lets you use, and the server runs the query as that account, so a schedule or an agent can refresh it. The server refuses a run as an account that Google does not let you use. With no runsAs, a BigQuery datasource cannot run on the server. On an org install with a registered database, a database datasource always shows the field, and takes a service account only.
• Composite charts: facet, repeat, and concat.
• Connector blocks: a line drawn between two blocks. The palette inserts every other block type. You write a connector in the Source panel, in a block's Properties JSON, or through an agent.

The Source panel edits the same JSON that agents edit, so anything an agent can write, you can write there too.