Hi Alfonso 

Thanks for posting in the community! Unfortunately creating custom hotkeys or shortcuts is not currently supported in Lucidchart. However I think that's a great idea! Would you mind adding your thoughts to our feature request form? Ideas submitted here are passed along to our development team for their consideration and hearing from users is an important way to help prioritize improvements to the product. 

Currently the best way to set default styles is by ensuring that no existing shapes are selected then adjusting your style preferences in the toolbar at the top of the editor. After doing so all additional shapes will be added with that default style. Please feel free to let me know if you have any additional questions!