Because Items can be (and often are) interrelated with other records in a database, you need a way to find out where one Item is used to understand the ramifications of modifying it (or, in the event you want to delete it, removing it from those related Items).
Master Items can be used in Condition Assemblies, Mixtures, and Chains. You can see where an Item is used by right-clicking on it in the Master Item List and selecting "Show Where Used".
Depending on where the Item is used, you will see one of the three lists populated...
Condition Assemblies
Condition Assemblies are groups of Items that are saved in the Masters. You "drop" an Assembly into a Condition to add several Items, preconfigured for a particular type of Condition, into the Items Grid. The Items update based on the settings in the Assembly. See Related Articles for more information on Condition Assemblies.
Double-click on one of the entries to open that particular Condition Assembly (Master)...
Notice the "Next" (and "Previous") buttons? They make cycling through the list of Condition Assemblies (where the target Item is used) very efficient.
Mixtures
Mixtures are a specific kind of Item that is made up of other Items to produce a "Yield". See Related Articles for details on Mixtures.
Double-click on an entry to open the Item in which the target Item is part of a Mixture.
Again, there are Next/Previous buttons to quickly cycle through the list of Items where the target Item is used.
Chains
Chain start with a "lead" or "head" Item that is dropped into a Condition pulling the "Chain" of related Items with it. See Related Articles for details on Chained Items.
Double-click on an entry to open the Item in which the target Item is part of a Chain.
Again, there are Next/Previous buttons to quickly cycle through the list of Items where the target Item is used.
Multiple Uses
An Item could be used in a Condition Assembly, a Mixture, and a Chain, as shown below.
You need to update its reference wherever it is used before you can delete the Item.
When you use the "Where used..." search, if you have the Items List filtered in any way, only those results are searched for usage in Mixtures and Chains. To search all Items, remove any filters from drop-downs or Search box.
Items - Overview and Video