> There were times when I want to be able to start working on some code on my laptop, pause, then continue work on my tablet later on

In order to do these things 'cleanly' (with a truly unified view of the entire "system"), you need some sort of process migration infrastructure that even Plan9 and Inferno don't really give you, AFAICT. Projects like OpenMosix and OpenSSI attempted to provide this, but I'm not sure to what extent they were successful, given that they've all been abandoned and bitrotted. Today, one might try to do the same sort of thing while also taking advantage of the new kernel-based namespacing that Linux provides, which might make some things somewhat easier.