Styriam Shaped Curves Merger

This add-on is meant for joining curves with shape keys. Normally, curves can be joined with Ctrl+J shortcut but using this on curves with shape keys leads to a loss of animation data. Fortunately, this add-on can merge curves and copy shape keys along with their f-curves and their modifiers.

Select curves in object mode and find Join Curves in the Object menu or in the context menu (right click). The active object becomes a base object for the merge and retains its modifiers and constraints.

In the add-on preferences, you can find an option to hijack the Join shortcut. When enabled, curves with shape keys will be merged by the add-on using the Join's shortcut (Ctrl+J by default).