Thou shalt build up and adopt toolkits with common tools
Code which is used very often should be made available centrally, if possible under a single package (ex: ZTOOLS) so that it’s easily identified.
There is a lot of code already available on the Internet to accomplish several common functions (ex: ABAP2XLSX). Adopt it;
For your most common tasks, develop your own tools which you can reuse and add them to the central library;
Advertise the existence of that library among your colleagues to avoid that they waste time come up with duplicate code wasting;
Whenever you develop specific code which you think can one day be reused somewhere else consider making it more generic and add it to the central library.