Hi everyone,
I found a way to select multiple rows in the Calibre library on my Windows 10 touchscreen tablet PC! Even works across multiple scrolled screens!
The problem is with the Microsoft Windows 10 onscreen keyboard. It doesn't do a very good job of mimicing a physical keyboard. I solved the problem by installing an alternate Windows 10-compatible keyboard on which the SHIFT and CTRL keys lock like a real physical keyboard. Selecting a row by ROW NUMBER, locking SHIFT, scrolling down, and tapping the desired ending row number is working fine for me to select consecutive rows. CTRL works for non-consecutive rows.
Just make sure you select by row number or you may unintentionally edit your ebook data.
I am not in any way affiliated with any onscreen keyboard software products and hope it's ok to post a link to the one I'm currently using. There are a bunch out there. The first one I tried,
Free Virtual Keyboard, works great and is small enough to keep out of the way as I work on my library.
I'm using an Acer Switch V 10 tablet PC and have not tested on anything else, but I hope this approach may be useful to others who are struggling with Windows 10 touch screens.