That’s what I usually do when I want to edit a stl. I know Fusion and Tinkercad can work with a mesh directly – but I generally prefer having the full geometry recreated natively since it opens up more options for modifications.
Here’s a little video I did showing the basic process in Onshape:
Once you get the hang of it it goes really quickly. I’ve actually redone some very complex designs in an hour or two.