Hi Filip,
Based on my understanding, it seems that you are facing challenge in retrieving data from the generated fig file. To assist you with this issue, I would like to suggest the following code snippet for your reference:
fig = openfig('F1slab_v1.fig');
axObjs = fig.Children;
%Since first is the colormap, select next 2 objects
dataObj1 = axObjs(2);
dataObj2 = axObjs(3);
%Based on the figure type select line, scatter, contour, etc
lineObjs = findobj(dataObj1, 'type','contour');
%Extract the x,y,z, etc data associated with the figure
xdata = get(lineObjs,'XData');
ydata = get(lineObjs,'YData');
zdata = get(lineObjs,'ZData');
Similarly, you can extract data from the second object and continue with subsequent operations or generate visualizations based on the extracted data.
For more information about MATLAB graphics object, refer to: Graphics Object Hierarchy - MATLAB & Simulink (mathworks.com).