That "do not modify" text is usually in the name of folders which contain the macros for object you downloaded from bimcomponents.com, if I remember correctly.
If you know you don't use those objects, then you will not need this folder either so you can delete the whole folder.
What I usually do is I remove the folder and check if it results in a new message missing something from that folder. If it does I add that object back or add the folder back if needed.
Karl is probably right about having to reserve the object (or its containing folder) to be able to delete the object from the embedded library.
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac27