Ofcorse, note that editor it self is coded in the engine, so same as editor edits things you game can do that to. You don’t need to make mashes, you can alreayd do things with existing build in shape meshes.
But if you really want to there procedural mesh component, which allows you to decelere mesh as much as you want
You probably want to know how meshes are made in technical way first if you dont knowyet .
There is no tool handling on runtime, all edit tools you will need to make by yourself. You can not use any code from editor on it as it is 1. not available either way by default 2. Not alowed by EULA