Hi.
I add leaflet v.1.4.0 to extension. Please, open component options and set “Leaflet version” list to “Default“.
In this case will be used the last version of leaflet in component. If you want to use the special version – select it from drop down list.
In paths I added new tab “Grid Layer”, now you can use it.
Here example https://joomla.zhuk.cc/index.php/zhosmmap-main/om-demo/om-features/om-feature-full-screen