MYSQL 8.0 server not found in Workbench directory in Windows 10?
MySQL server and MySQL Workbench both are installed in the default location ("Program Files" for 64bit apps or "Program Files x86" for 32bit apps). MySQL Workbench however only exists as a 64bit arch build.

Did you check the server path actually exists? If it does not you may have forgotten to install the new server. Simply run the MySQL Windows installer again and let it install the server.

About the left behind ProgramData content: that's probably a safety measure to avoid deleting your data unwantedly. If you don't need it anymore then just remove the 5.7 subfolder.