If you’re compiling the game yourself, you can now get an experimental, unfinished z-level build by adding ZLEVELS=1 to the “make” line. It doesn’t do anything interesting yet.
Not sure if it’s a good place: my semi-old PR got skipped in the last “merge wave”, probably due to being buried under other PRs. I first sent it with [WiP] name, so I guess it wasn’t queued. Now I think it is ready for testing.
If the above PR gets in, modding multiple use items will not require touching source code at all. For example, toolbox could be easily changed to display a menu with “reinforce with tape” (from basic repair kit), “pull nails” (hammer), “saw metal” (hacksaw), all 4 knife-related functions and “saw logs to planks” (wood saw).