Actually figured out a way via CSS. Just type the following code into your Custom CSS field:

```
@media (max-width:1210 px){
.sp-megamenu-parent > li > a {
display:none;
}
#offcanvas-toggler{
display: block!important;
}
}
```

Note that:

- This makes that your megamenu parent disappears, and your offcanvas toggler appears at a screen size of 1210px and below (which is perfectly the longest size of my main menu in the language with the longest words)

- ".sp-megamenu-parent > li > a" and "#offcanvas-toggler" are the css-names of my main menu and offcanvas menu respectively; make sure you type in yours to make things work for you equally well. 

Cheers!