If you create an Escher Python widget with a custom reaction scale, the scale will not appear right away:
escher.Builder(
map_json='iJO1366.Central metabolism',
reaction_data={'PGI': 10, 'GAPD': 20},
reaction_scale=[
{ "type": 'value', "value": 10, "color": '#41b6c4', "size": 20 },
{ "type": 'value', "value": 20, "color": '#2c7fb8', "size": 25 },
],
)
The workaround for this bug is to open the settings menu and click the accept checkmark after the map loads.