As Jason indicates, there is no export/import feature at this time. Flexera Services uses an Excel CSV template and a custom PowerShell script for bulk loading catalog items. If you are able to export the data you want from the WD_WebPackages table into a CSV file, you could write a PowerShell script leveraging available API's (https://helpnet.flexerasoftware.com/appportal2015r2sp4/default.htm#helplibrary/AP_APIRef.htm) to automatically create catalog items using the data from the CSV file. Keep in mind that things like SCCM package ID's/program names and Application CI's will be different if connecting to a different SCCM instance, so you'll need to account for that.
Note: This original post is referencing App Portal 2015 R2, so the link above points to the Configuration Guide for that release; however, there have been quite a few new API's added in newer releases, so be sure to check the correct HelpNet Admin/Configuration Guide for your release (or go to the /esd/api.asmx and /esd/ws/integration.asmx pages on your server) for the latest available information.
As for workflows, approval groups, questions, etc., that gets quite a bit more complicated to migrate. I have dabbled with writing some complex SQL queries in conjunction with the SQL data export/import wizard, but this is a very involved process prone to error, so unless you're super familiar with SQL and the App Portal database schema, you are probably better off recreating these by hand in the console.
Site settings can be migrated fairly easily by exporting/importing the WD_Config and WD_AppSettings tables within SQL. But since these settings do contain server names and file paths and such, just be careful to update those entries to point to the right places for your new server.
