@office6PUWT you'll need to double click on the sub-assembly in the tree that the file belongs to first. You can't delete the children of sub-assemblies in the master iam.
Another possibility is if you have opened express mode (under the assembly ribbon). Some functionality is restricted with this on.
Use iLogic Copy? Please consider voting for this long overdue idea (not mine):https://forums.autodesk.com/t5/inventor-ideas/string-replace-for-ilogic-design-copy/idi-p/3821399
