From Smart P&ID 2019 HF8, an administrator or a user with read/write access to the Symbols folder can generate images for the symbols so that when a user with read-only access opens a drawing for the first time, Catalog Explorer loads images for all symbols in a plant.
Symbol images are automatically generated when the reference data is upgraded, but when a new plant or symbol is created or when you make changes to the symbology in the Icon layer and you want those changes to be reflected in the symbol images, you must run the Generate Symbol Images Command.