Just saw this and really like the idea. Going to try it out, just the fastener and drill tables are super useful. However it seems like this sort of tool is somewhat specific to industry/project, which may explain some of the limited use by others (eg I'm in aerospace, so I worry about cryo and elevated temp properties a lot, for example). I wonder if anyone has ever made a "customizable machinery's handbook" style app where you can pick and choose what sections to include.
A couple pieces of feedback, I often want to look up material properties by material, rather than by property. It might be nice to have properties by material, a-la how matweb lists them. But of course I usually just go to matweb for quick references.
Have you ever read Foundations of Ultraprecision Mechanism Design? They have a section on material selection tables that are similar to the "stiffness/density" chart you made (but they have some really helpful and cool formulations). That chapter of the text might give you some good inspiration for other ways to present material properties.
I appreciate that you make all these tools and then share them publicly, it's very generous and helpful!