For example, I made a 10 x 10 grids by using loop cuts on a square plane, now I would like to make it to 20 x 20, is there any way I could change the grid instead of doing it from the beginning? thanks a lot
Just subdivide the mesh. It will create a new edge in between all edges.
From a single subdivision, a 10 by 10 grid will become 20 x 20.
Select all edges (press A).
From the menu, select Edge > Subdivide
Or you can do this from the context menu. Press the right mouse button and select subdivide