Is there any way to export annotations in Json format in 3D slicer?

Operating system: WIndows
Slicer version: 4.10.0
Expected behavior:
Actual behavior:

Yes, you can do it by a few lines of Python code (that you can either copy-paste to the Python console, in a Jupyter notebook, or in a scripted module). For example, export markup fiducials into a json file:

markupNode = getNode('F')
outputFileName = 'c:/tmp/test.json'

data = []
for fidIndex in range(markupNode.GetNumberOfFiducials()):
  data.append({'label': markupNode.GetNthFiducialLabel(), 'position': coords})

import json
with open(outputFileName, 'w') as outfile:
  json.dump(data, outfile)

Hi, Can I export segmentation results into json file?

Do you mean writing the 3D voxel array? Of course, it is easily doable, but it would be terribly inefficient.