1. If you drew an object that you didn't intend to draw, use the eraser to remove it instead of undo.
2. If you did a push/pull operation no that you didn't want to, do a second push pull operation to get back to the original position instead of undo. Note you can type distances for operation or snap to other geometry.
3. If you deleted an object you didn't intend to then redraw it instead of deleting it. If you deleted a lot and don't want to re-draw it you can close the model without saving and reload the last saved version.

One additional note I will add. If you are just drawing loose SketchUp geometry that isn't part of the OpenStudio model yet, such as a floor diagram that you plan to later extrude, you can use undo.

If you want to use undo, you should just keep working with Sketchup objects instead of OS objects, while in Sketchup.

Check out the Experimental Workflow scripts named similar to Make Sketchup Groups From Diagram, and Merge Sketchup Groups into Osm.

instead of building the building out of OS objects (with different colors for walls and floor etc.) build it out of Sketchup objects (plain colored), and when is all and said and done for creating the form of the building use the "Merge" script to convert the Sketchup shapes into OS spaces and surfaces.

Use the selection tool to select a line segment of the surface that needs to be removed and then use the eraser tool or press the delete key. Then redraw the correct surfaces or subsurfaces.