Thank you @popey. I did install your warpinator snap from beta channel and looked at snap.yaml. I saw you used core20 but when I tried it with extensions method, it said that extension gnome-3-34 is not supported yet, so I went with desktop-helpers method. Since snap.yml did not have ‘parts’, I combined the ‘environment’, ‘command-chain’ from your file and ‘parts’ from my file. Still doesn’t work (while your snap works). Will use your snapcraft.yaml file to locally build and check.
BTW, there is a interesting discussion regarding python plugin, which may help me. Will check that as well.