Hi Andreas,
I am fresh to the Zettelkasten method, even though many of its aspects are similar to the way I work. Soon I’m going to decide which tools I do want to use - both my intuition and some thoughts lead me to the desire to do it with pen & paper instead of a digital tool, which brought me here via a web search. Ideally, I’d find a way to combine the best of both worlds, willing to accept some extra time effort to keep it synced.
How’s your approach in the meantime and if you do use a digital tool, how which tools do you use?
Regarding GTD: I tried them all (wanting to develop my own GTD solution a while ago) over a couple, at least all of the products which are basically suitable for applying GTD. I used Things 3 and 2Do for more than one year, these are ranked on place 2 and 3. For me the best tool is FacileThings, it is specifically designed for applying GTD strictly and for utilizing efficiency bits, like codes for projects. Projects support defining the outcome, horizons range from purpose down to next actions, with alignment etc. etc.
For more than years I did not use a digital tool for GTD as well, I did it with my Bullet Journals and with what I do call a “Meta Journal” (registry for all horizon elements, with code system for fast and easy reference). The reason was that all of my digital GTD endeavours ended up with massively bloated systems - now I know that this happened because I was looking for something like Zettelkasten without even knowing the concept and was mistaken by thinking I could handle all my ideas also within my GTD system. So now I safely returned to FacileThings, but still do use my Bullet Journals and my Meta Journal - these three tools in combination work fine, soon to be enhance by my Zettelkasten to be.
Cheers
Günther