@Truck @neauoire
Likely less relevant for you, but I'll add it here regardless:
MSX Application Templates for MS Visual Studio: https://www.msx.org/forum/msx-talk/development/msx-application-templates-for-ms-visual-studio

https://www.msx.org/forum/msx-talk/development/first-step-to-learn-msx-assembly has some further links.

#EricMaas was also working on a #gdb like debugger for #MSX programs written in C, compiled using #SDCC, but unfortunately the project seems abandoned: https://bitbucket.org/erik_maas/openmsxgdb/src/master/