How to CHANGE things later

Ok… This is a Newb question, that I hope is something stupid that I am missing. How to I CHANGE something, after the fact?

A very simplified example:

I design very simple square “washer” like object. 1inch square, with a 1/4inch hole in the center. camphor some edges. Print it out, GREAT! But… a 1/8 inch hole would be better …

I can not figure out how to go into the drawing/model , and ONLY change the size of the hole! All i can do, is either keep hitting the “un-do” button, until I get to a point before i did any extrusions, or start from scratch.

Starting from scratch, for something as simple as what I described, is no big deal… but for larger, more complicated projects… not so much.

PLEASE, tell me I am missing something very basic?

MW

So- first zoom in tight. Then select each of the four inside faces of the square hole by tapping it once. Then invoke the SCALE tool. To make a 1/4” hole into a 1/8” hole, scale to 50%.
You can also invoke the move rotate tool to MOVE the hole anywhere in the face of the object its cut thru.
No need to go into sketch plane at all.

Good point @Sculptingman! If you need to make just the hole smaller, for example, you can use the advantage of direct modeling. Grab one face and move it to meet the dimensions you are looking for