Hello there, i couldnt find any option to pause time inside the sandbox, is there any way to do it? could you explain how?

Thanks in advance

That is not possible.

This mod lets you slow dime time a lot as a workaround: https://mods.factorio.com/mod/TimeTools

Why isn’t it possible?

Would it be possible in single-player?

It simply is not possible, due to how the game engine works, and I doubt it ever will be. That is a fundamental trade-off of using this mod for in-game designing - if you don't want time to pass in the game, then you need to use a different world/save to do this.