Can you change the designated goods after Trademark registered?

Yes, but you will need to file a new application for new goods (or services) that are outside of the description already submitted. In other words, you may "narrow" the description, but not enlarge it.

For example, registered "computer software", may change to "computer software for doing XYZ" but may NOT be changed to "computer hardware and software", and the computer hardware will need a different registration. (in the USA anyway).

Many companies of dozens of registrations, each of which cover only a small segment of the goods and services marketed under the same (or similar) mark.