the clipping distance in Sketchup is mostly related to the size of the model.
if you have a model with objects 1km distant from each other, your clipping distance will probably be greater than 30cm.
Reduce that distance to 100m and the clipping distance will be 1cm.
So the zoom extends button is good to check if there are no small objects LOST very far from the main model and hindering the clipping distance.
If your model is on purpose very large and you need to edit small objects, maybe it´s ideal to copy the object and paste it on another Sketchup window, edit and return it. Or maybe use with Components and edit them outside the model and have them update automatically, etc.