After searching endlessly I finally found a way to make the tiny scrollbar in Opera(38) wider. This has been bugging me for a long time so I thaught I would share this.
To increase the scrollbar in windows - open regedit and go to
HKEY_CURRENT_USER - Control Panel - Desktop - WindowMetrics
Right click and edit "ScrollWidth" and put in -400 (or more if u wanna) - close regedit and log out/in of windows - now you have a wider scrollbar everywhere in windows 10 - but NOT in Opera ! - BUT - start Opera - and type in "opera:flags" in the adress bar - and there you will see:
Alternative native theme
Enables an alternative native theme implementation on Windows 8 and above.
Choose disable - restart Opera - voila - Now Opera uses windows metrics WITH wide scrollbar.
HALLE finally LUJAH.