Hi there!

I just encountered this problem and found a way you could handle it at the moment (maybe this is already known and nothing new): I write the measurement and divide it then with the scale. For instance if I want to draw 1m in a 1:20 scale in Layout, then I draw the line and type: 1000/20 and hit enter (1000 because of the mm - you can change this in the settings).

I know it might seem like extra work but it after 5 minutes became second nature to. Sure this is no ideal solution and an upcoming Layout feature has to be quite complex, interacting with the viewport and so on...

I'm also not sure if this works with feet, just tried it with metric measurements.