You can search files and folders in your (connected) online store when accessed via NSCM. To open the search panel click the option “Search” in NSCM top bar:
To search files or folders a specify keyword and click the search icon at the right of the field. The results will be shown in box below. In case of OneDrive the list will include also the files whose content contains the keyword. Search takes place among all folders in the store. To open a result just click it. To open a folder which contains a result just click the folder icon at the right of the result.