Hi Ingo,
Can you create a freely editable wiki for named "Developer guide & tips" ?
Also, someone (you ;-) ) should have the ultimate rights to lock/unlock it whenever appropriate so that it will not be edited all year around.
I suspect it will be edited a lot because it is still young and new tips will be added frequently or current content gets revised.

According to suggestion;
We can start a WIKI in cforge called "Developer guide & tips" which can contain a compendium of good practices like versioning tips, coding style tips etc etc.

Versioning tips;
-All developers should stick to one version of the development environment to avoid any confusion (not only for libraries). Offcourse, users can use any version.In any case, the user must know project (library) format before download. This format must be one for target device (RPi3, ...).
- "used compiler version" and "project file format" are different things. You can e.g. use 3.5.10.0 version as compiler but e.g. 3.5.11.0 version for the project file format.
- As long as your project is not finished, stick to the chosen version of compiler and project format;
- ;
etc.

Coding tips;
- for RTS_IEC_HANDLE and RTS_IEC_RESULT types need to add SysTypes2 Interfaces (3.5.4.0);
- if possible, use standard error codes (CmpErrors or CmpErrors2 Interfaces);
- avoid using dynamic memory (the usage of NEW operator);
- use the ST language whenever possible (ST is by far the most versatile language, in which all operations, manipulations and functions are possible);
- document the source code (add meaningful comments);
- for modern coding style advice: read the Codesys v3 library development tips as provided in codesys help - guidelines for creating libraries,
They are pretty good but, but not as thorough as "code complete" but provide a very good starting point.
Further reading: e.g. Steve McConnell "Code Complete";
-;
etc.