How to force a view refresh without having it trigger automatically from an observable?
You can't call something on the entire viewModel, but on an individual observable you can call myObservable.valueHasMutated() to notify subscribers that they should re-evaluate. This is generally not necessary in KO, as you mentioned.
In some circumstances it might be useful to simply remove the bindings and then re-apply:
ko.cleanNode(document.getElementById(element_id))
ko.applyBindings(viewModel, document.getElementById(element_id))