Having not yet upgraded an existing WAB Dev Edition install, is there a process/workflow that I should follow to upgrade existing sites built with a previous version?
you can import an older version WebApp via the following:
Create and import app—Web AppBuilder for ArcGIS (Developer Edition) | ArcGIS for Developers
Also Upgrade apps—Web AppBuilder for ArcGIS (Developer Edition) | ArcGIS for Developers which you would probably see in the TOC on the link Tim provided.
and, although I need to review/update this.. Tips (LocalLayer widgets) for more customization and Updating (may help with others too)
I upgraded my apps using the instructions above and it worked well. It will copy over any custom widgets, but you'll still have to make any necessary customizations that you may have made to any files that aren't in the custom widget folder.
I noticed that the instructions on this page Upgrade apps—Web AppBuilder for ArcGIS (Developer Edition) | ArcGIS for Developers
are just slightly wrong. In step 4 where it says "type node ....", you'll want to use node_64 or node_86 depending on whether you have a 64 bit or 32 bit system.
That is a great point to mention if you did not install NodeJS on your machine as the Getting Started page states otherwise just using node would have worked.
Because Web AppBuilder runs on top of Node.js, you must have Node.js installed on your computer. The download package contains the Windows version of node.js.
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