In case you do not remember the API, so try the following (for the example of Hyperlink feature).
First usually quickly look into the test of the source code, such as via command line:
git clone https://github.com/tdf/odftoolkit.git cd odftoolkit/odfdom/src/test find . -name *.java | xargs grep hyper
Here: The results are just within the changes packages, which is the new Event API (similar to SAX) only supporting ODT (not ODS yet).
What is always working is to use the DOM API. But you need to know what XML is being used for your feature! Test it! You may use LibreOffice to add a simple hyperlink in a cell save it, unzip it and take a look into the XML.. (JEdit with the Archive is able to edit & save XML from within the ODF ZIP. Its XML Indent Plugin helpful to pretty-print, but not ODF conform (might insert whitespaces). Therefore, a Visual Studio Code ODF extension to edit ODF XML would be very tempting)
There I find my test file and you see how a hyperlink works:
<table:table-cell office:value-type="string"> <text:p>Next a hyperlink: <text:a xlink:href="https://tdf.github.io/odftoolkit/" xlink:type="simple">some text</text:a></text:p>
Now, when you know what is the XML node you might look into the ODF specification for more information:
All ODF XML is reused across the ODF document formats, therefore Hyperlink XML is the same for ODT and ODS
Any XML element/attribute is represented by a Java Class as the "typed" DOM node by a simple pattern. For instance, the XML element text:a will become https://github.com/tdf/odftoolkit/blob/master/odfdom/src/main/java/org/odftoolkit/odfdom/dom/element/text/TextAElement.java
Now you might check in your favorite Java IDE [for instance, Netbeans, IntelliJ and VSCode) what classes are using this class. By this, you will see that the parent DOM elements (e.g. TextPElement) have a function to add a Hyperlink.