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You can use any square shaped SVG or PNG file as a symbol. These have to be added to the System/Symbols folder in your Metview home directory. On top of that you can also use symbols from the directory specified by the METVIEW_EXTRA_FEATURE_SYMBOLS_DIR environment variable. When you start a uPlot window it scans this directory these directories and adds all the files with .*svg or *.png suffix to the Markers and text group in the Symbols sidebar.
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