Assuming you use the plotly charts in the advanced tab in Mendix you can set the mode to advanced.
There you can add the following code:
This will set the y axis fixed from 0 to 100 for example. See also this cheat sheet: https://images.plot.ly/plotly-documentation/images/plotly_js_cheat_sheet.pdf
or this one: https://docs.mendix.com/refguide/charts-advanced-cheat-sheet#1-introduction