Editing many items at once, and moving an item list between projects.
The Manage Items window is the item list with room to work: the whole catalog in one grid, with an add row, each item's included children in its row details, and import and export on the toolbar. Use it for the setup pass at the start of a job, where the panel suits working item by item while you draw.
Items sort into three groups, which is a reading aid rather than something you set:
An item moves between groups on its own as you attach and detach children. See Assemblies.
Select several items and the editor opens in bulk mode, applying one change across all of them: re-unit a dozen items, set a multiplier on a whole phase, recolour a group.
A blank field means "varies", and leaving it blank keeps each item's own value. Where the selected items disagree, the field opens empty rather than showing one item's value and quietly imposing it on the rest. Only fields you actually fill in are written.
Selecting a single item opens the ordinary editor instead.
Export writes the item list to XML: the items, their settings, and the inclusion edges between them. It is how a standard item list moves to the next job, or gets kept as a company template.
Import offers two sources.
A list exported from this app. Imported items are given fresh IDs, and the inclusion edges are remapped to match, so importing the same list twice cannot produce duplicate IDs or cross-wire one import's assembly into another's.
Lists exported by much older installs, which stored items and sub-items as two separate lists, are converted on the way in and keep working indefinitely.
An .xlsx or .csv. Because a spreadsheet has no fixed shape, importing one opens a column
mapping step: you say which column is the code, which is the name, which is the unit, and so on.
This is how a bid schedule someone sent you becomes an item list without retyping it.
The file is read and validated before anything is cleared or inserted, so a malformed file fails with a message and leaves your existing list untouched. A bad import cannot cost you the list you already had.