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Asset search field: Search for asset number and asset name. Shows items connected to selected asset/structure. Search Selected Tree Only: Only generates hits for assets in selected tree.
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Item can be connected to
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asset using this button.
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Remove item from asset with this button. Alternatively also from the asset card (in edit mode).
Alternatively, new 
New items can also be created directly from the asset card (in view mode) via a separate plus this button.