You need two open-curlies {{ at the beginning to avoid starting a Relevance Substitution.
You only need one close-curlie } at the end, because you are not inside a relevance substitution.
If this were inside a relevance substitution and needed to include a literal “}” as part of a string, you would have needed to escape that as “}}” to avoid ending the substitution early.
I will also say that what you’re trying looks unusual…not sure why you’d need to manually copy files into InstallShield’s cache area, but be aware the copy will also fail if the target file already exists, so you may need to use the ‘delete’ command first before trying the ‘copy’ command. ‘copy’ will not automatically overwrite an existing file.
need to copy file “uninst_setup.iss” under this {4D9CA1B8-5FF5-47A7-8BDF-C37D1F9F55A5} directory that’s comes under “C:\Program Files\InstallShield Installation Information” folder
You need to give the full pathname (including filename) on the copy command.
Also, possibly an artefact of the forum, there seems to have been a backslash dropped from your original path (hint, use the </> button to format lines of script)…