Ideate Explorer can be used to select Revit elements within the same category but with differing family:types for the purposes of swapping or merging types. A common example would be to take all of your lines from an exploded DWG and then merge then onto the Medium linetype.
NOTE: For lines, instead of using the Properties palette, look for the Line Style selector from within the Modify | Lines tab as shown. You can use the Search text filter to quickly find all Lines that include any keyword, e.g "hidden-".
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