In my DOSBox-X-App for the Mac (search for it on Google), in the Mapper Editor, Mod3 is the Mac Command key. I don’t remember what it is in default DOSBox-X. Also, my DOSBox-X-App runs in native M1 mode on Apple Silicon Macs. I built it from my slightly customized version of the code for the December 1 release of DOSBox-X (the version that Wengier announced in the first message in this thread).