You can search for content using a prefix of 'Code: ' + the code (or partial code) for the content you are searching for, for example, in the UK Uniclass Work Sections content set, searching for Code: ss_15_30_90_86 to find the 'Timber section repair systems' clause, or, Code: ss_15_30_90 to find clauses in the 'Timber repair and renovation systems' group of clauses.
Whilst it is still possible to search using a 'Code: ' prefix, the platform now includes the 'Browse content' feature, which provides an improved user experience when you wish to locate and add content by code.
This feature is available in all content sets.
The use of this feature is covered in detail in the 'Browse content set' section in the separate Searching and browsing the content set support article.