On the old crap, while working on very accurate details and texture placing, the zoom level of 400% and 800% were useful to draw linedefs.
DB2 seems have a 200% maximum in the taskbar, may those zoom levels come back in a future release ?

You can use the mouse wheel to zoom in to 2000%.

Thanks for the answer, I'm using laptop for the last 4 years with DB1 almost on keyboard only and the integrated mousepad (without roll) that cut off several functions to draw sectors.
Now that I switched for a more decent machine and turned to DB2 where this zoom over 200% was missing.
Request is maybe too specific for this keyboard only use, you can lock the thread.

The mouse wheel is just the default, you can bind the zooming to other keys in the controls preferences.