Yes, something like predictive text with pop-up explanations and syntax examples much like in MS-Excel, as you start typing a formula (e.g., =count... then all the count variations and expression forms appear). In anycase, some kind of expression builder with help. M8 had predictive text when building functions, the possible field names or function names would appear.
I attach two screen shots, first is in Manifold Future where I add a field, set to a real number, and do a search for "area" hoping I'd find the likely function or query. But I get an error. I did this once before months ago and I think I have to replace some of the text in quotation marks with something particular to the table, but I don't remember exactly what. Some popup help would be useful. I know I should RTM, but this is a quick query, I just need to send an email and tell someone the area. The email is the task, not the GIS task.
Second screenshot is from QGIS, I click away at the choices that appear and build my expression. There is some help text. I got it first try to show square metres. It's an easy next step to divide by 10,000 to get hectares. I see a preview of the calculation, 8411454.4 ha. Done. Sent my email, back to work.
The expression builder in Manifold Future and R9 is a huge step forward compared to M8 which I never used to full potential using queries or functions. Building on MF, help text and example expressions would be really helpful. Also if the dialog window could show a preview of the intermediate result of the expression as it is being built would be helpful as confirmation the expression is being constructed correctly.
Another idea, in building expressions in MF, some arguments are optional, what if when the user does not change the default value for an argument text, say "tolerance" that either the optional argument falls away or is set to some default value? This happens in MS-Excel, for instance when calculating PMT (interest payments, the default is interest charged at the beginning of the period, by entering a "1", interest is charged at the end of the period (I don't remember exactly but it's explained in the popup help text). If I don't specify when interest is charged, it defaults to the beginning of the period which is the most common situation.
Area expression QGIS.JPG