Hi,
in order to be able to download the add-on tools directly in CODESYS you need a higher version, which includes at least the CODESYS Package Package Manager. This function enables to install the add-on tools.
In case this is not possible you can nevertheless benefit from at least some of the add-on tools, e.g. the CODESYS Test Manager:
Download the latest version of the CODESYS Development System for free from the CODESYS Store:
https://store.codesys.com/engineering/codesys.html. Furthermore, you can download, install and license the CODESYS Test Manager (see
https://store.codesys.com/codesys-test- ... -demo.html) directly within the CODESYS Development System (there is a free demo license available).
Open the exisiting CODESYS project with this latest version and test your application code automatically by means of the add-on tool. It offers a dialogue based configuration, as well as unit tests by means of test source code or test tables. Ypu can use the results and work with them in the version from your device supplier.
Of course this is not the smoothest way of working, but in any case you have an option for doing so. Perhaps, you can even automation some of the steps by means of the integrated Python interface. This will work at least for the add-on tools Static Analysis and UML (at least for some parts of the functions) in the same way.
And of course it could make sense to motivate your device supplier to make an update. There are many, many new features and bugfixes included since V3.5.06, furthermore security vulnerabilities were closed, performance was increased etc.