Back in binary mode, it was very common to have 4D Remote clients have read-write access and edit anything related to code, forms, and structure. When project mode was initially introduced, this behavior was changed to have 4D Remote cilents have read-only access and was not brought back until 19 R6 or newer.
Be sure to use the current R release to be able to develop code via 4D Remote. To do so, have the 4D Remote client connect via Custom tab and check the "Activate development mode" box. Also make sure the .4DProject file is accessible to the client.