While waiting for a tutorial from @FelipeDelRio, I’m trying to reverse engineer the process he used 
I don’t know if I got it right but I got at least some results, convoluted as the approach may be.
If anyone has an improvement, please let me know!
The blend file: Geo-nodes array v7.blend (3.5 MB)
I found a much simpler setup using Line primitives, which also removes the upper limits.
Has anyone found out how to ‘chain’ the XY axis geometry output to the Z-axis?
Blend file: Geo-nodes Line v2.blend (1.3 MB)
Update: I found Felipe del Rio’s solution on developer.blender.org
Felipe uses the Grid primitive, which gives you a 2d array option. No ‘chaining’ required.
I’ll wait for further developments to see if instancing geometry becomes an option.
Nice 
Wow that’s awesome!!! Any buy/download link?
Hi everyone, thank you for the comments!
I edited the post with links for download! 
Wow, thank you, that’s very generous!