Thank you for taking the time to help. I have a model in my Blender workspace that came from the source subdivided into four individual meshes/armatures/materials. I merged the meshes into a single mesh, and set up the new, single armature the way I wanted it. I exported the collection as an FBX, but when I import that FBX into other programs, it's still showing up as four separate meshes. How do I get Blender to export the collection as a single mesh/armature?
Like FFeller mentioned, select all the objects, right-click, and press Join. Make sure you shift click one of the objects so that at least one of them is selected, otherwise it is impossible to join them.
In the FBX export screen, there will also be an option to export only "Selected Objects", or just the "Active Collection".
Select the objects and collections you have to export, and tick both of those. If are still having problems, maybe export the objects as OBJ and everything else as FBX.