When I trim the blank using IGES file, there is a message such as “Entity type xxx form 0 not supported # lines = x”. What does it mean?

It means that one of the entities in the IGES file is not supported by LSDYNA. If you encounter this problem, you have two choices: a) send it back to LSTC with your IGES file; and b) use other software to read the node and its coordinate, and then define a trim curve by x and y coordinate.