I managed to make it work follong the instructions given https://groups.google.com/g/mapstore-users/c/oiWzXMtDe04
on this thread. Once I made it work, my main problem was that I needed to have that map in the main maps list, so I created the map creating a mymap.json (modifying new.json) and then saved it so it appear in my maps list. The main problem is that when you save it, the Refresh tag disappears, so you have to edit the database directly, which is not very comfortable. The saved maps are stored in the geostore.gs_stored_data table from the database and the tag used to refresh is ,"refresh":10000 as said in the thread. For me, the main problem is that when you do a modification in the map, let's say, add a new layer, and save it, that tag disappears again, and you need to add it manually again. Maybe it could be a nice improvement to leave that tag there, but it must be something with the save map tool, and I don't really know how it works.