Any scripted approach that worked in with your locally installed SAS version will still work under SAS Viya (Compute).
The big difference for you will be that you need to use directory paths that are accessible to your remote SAS server - which is not a local path. You can try a path that you see under Files in SAS Studio.
If you want to export a table that's loaded into CAS then you can still use your existing scripts as long as the source CAS table is accessible via a libname that uses the CAS engine (if you can see the table under SAS Studio then that's what you can use). The process will then first pull the data from CAS to Compute and then create the Excel file on the Compute side.
If you want to directly write a CAS table to Excel you would need to use Proc Casutil or CAS action table.save
Using SAS Studio you can download files from the server to the client side by right clicking on the file to get the download option in the drop down menu.
