However, with the VuMarks, when I put more than one instance of them from the prefabs into the scene, Unity throws an error that he detects multiple objects with the same ID.
In order to solve that I need to set my VuMark objects in Unity to the custom IDs that my printed VuMarks have, but it seems like that is not possible?
Don't have two VuMark prefabs in your Hierarchy/Scene that are both set to the same VuMark Template. If you do, you'll get a warning like this:
Duplicate Trackables detected for: 'MortonTuxedos'. Only one of the Trackables and its respective Augmentation will be selected for use at runtime - that selection is indeterminate here.
This is similar to the warning you get if you try to have two "Stones" ImageTargets in your scene. Whereas with FrameMarkers, you do have a prefab instance in your scene for each FrameMarker instance, it doesn't work that way with VuMarks. For a single VuMark Template (i.e. MortonTuxedos), you will have a single VuMark prefab instance. That one prefab instance will handle all of the variety of VuMark Instances that can be generated from that VuMark Template. With FrameMarkers, the IDs were already decided and they were 0-511 with max of 512. ID 1 was linked to a specific pattern of dots, as was ID 2, and so on. With VuMark, if you have an ID Type of String and an ID Length of 4 and you use "abcd", you will get a specific pattern of elements in your VuMark Instance. "abcd" will always return that specific pattern. You can't use "abcde" because the max length for that particular VuMark Template was 4. When you enter "efgh", a different pattern of elements will be generated. So when Vuforia sees a printed instance of your VuMark, it looks at the pattern it sees and then calculates what the ID is from that pattern and stores it in the VuMarkTarget.InstanceId when the OnVuMarkDetected() callback is called.
Look at the VuMarkHandler.cs script in our VuMark sample app and you'll see that when a VuMark instance is detected, the registered callback will be passed a VuMarkTarget which has an InstanceId containing the Id that you specified from the Generate VuMark Instance Dialog in Target Manager.
The MortonTuxedos.svg (the SVG template, NOT an SVG instance) file is included in the VuMark-Designer-6.0.112.zip.
We have a lot of documentation on VuMarks. See our articles here.