Means to specify the number of significant digits in results. Example implementation in the attachment.
The results formatting of engineering computations should reflect their valid precision. Typically, this is assumed to be tree significant digits, perhaps 4 if the leading digit is 1. This is based on the precision of most available input data and in former times that was the achievable precision of the slide rule.
I find myself adjusting the number of digits in the right button menu on a case by case basis and have to correct the settings if Input data changes.
Currently, the only way to enforce a given relative precision independent of the result's order of magnitude is to set the exponential threshold to 1 and to specify the number of digits accordingly. However, the exponential threshold is better used to provide readablity than to control precision.