Docs: table column visibility

documentation/functionality/table_column_visibility.md

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+# Table column visibility (and exports)
+
+Most tables in the application let you **show/hide columns**. This helps when working on smaller screens and when
+exporting data.
+
+## Where to find it
+
+- In a table header, use the **column visibility** button (next to the export/download button).
+- Some columns may be always visible (they are not hideable).
+
+## What it does
+
+- Hiding a column only affects the current table view.
+- Exported data follows the **current column visibility**: hide columns you do not want included before exporting.
+
+## Tips
+
+- If a table is wide, hide non-essential columns to reduce horizontal scrolling.
+- Use the table help (`?`) for reminders about sorting, filtering, and export behavior.
+