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pt = window.get_output_panel("paneltest")
pt.set_read_only(False)
edit = pt.begin_edit()
pt.insert(edit, pt.size(), "Writing...")
pt.end_edit(edit)
window.run_command("show_panel", {"panel": "output.paneltest"})
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Open command pallet with;
ctrl + shift + p
Execute following command to install package manager;
"Install Package Control" + enter
Browse/search installable packages with command;
"Install Package" + enter
Once you find the package your want, highlight it and press enter
Done!