Please see: https://easyeda.com/forum/topic/How_to_include_thermal_vias_-Kr1ZljheA

I'm using KiCad for my design and have no trouble creating the via there; the question is about what options we have (and what results to expect) with the EasyEDA fabrication service. In your post you suggest that via-in-pad is not available with EasyEDA. What about a "tented" via, or a "mask plugged" via? KiCad creates tented vias by default, but I have read that the success of via tenting varies from process to process. In some cases the mask might not be viscous enough (probably not an issue with 0.3mm drill). In other cases there is a concern about contaminants being trapped inside the via.