writetable doesn't return any arguments, so that's what the error message is saying.
writetable writes a table to file. save saves variable(s) to file. Presumably you don't need to do both here.
function ExporttotxtButtonPushed(app, event)
[fn,pn] = uiputfile('Road Profile_fl.txt'); % avoid using 'path' as a variable name,
% since it is a built-in function
if isnumeric(fn) % user canceled
return % return early
end
% write the table to the user-specified file
writetable(app.UITable.Data,fullfile(pn,fn));
end
This presumes that app.UITable.Data is in fact a table, but it could be a matrix (in which case use writematrix) or a cell array (in which case use writecell).
