You can use many tools in Segment Editor to get rid of small vessels but preserve large ones. It is an independent question from glTF export and is discussed in separate topics on this forum. Please read recent topics related to lung and if you have trouble producing good lung vessel segmentation then you can ask for more help by commenting in those topics.
These are all unnecessary. What I meant is to simply decrease the “Reduction factor” in the OpenAnatomy Export module to a lower value to preserve more details. If you set the slider to 0 then the exported glTF file will contain the exact same details as you see in Slicer.
