Hello Pachner
Welcome to the forum!
As I'm sure you know, the handset/meter for the Combo doubles as the linked BG meter and requires a blood result to access the bolus wizard.
There are other bolus meter wizards (eg the Insulinx and Freestyle Libre handset) but these too would require a fingerstick.
If you are wanting a bolus calculator to bolus from a Dexcom G5 without fingerstick sample, then something like the mySugr one might suit you.
Any reason why you are wanting to avoid fingerstick checks with meals? All continuous data is subject to a bit of lag and there will always be discrepancies between fingerstick results and sensor data (even the newer systems). Personally I do the 4x (inc bedtime) checks with meals to keep an eye on sensor results and for calibrations - though my Medtronic is happy to accept keyed-in data for the bolus wizard, so I'd be able to go from sensor data alone if I wanted to.