I already set to default for all photos, videos and downloads to go to SD card. what's left are apps. I guess it's a limitation for phones with external storage.
before this I was using S6 edge with internal storage. this gave me a bigger storage to experiment new apps. with mate 10 I have to be selective on what to download.
Err, don't understand what you meant limitations for phone with internal storage. M10 (not pro) has 64gb internal storage plus external storage support. It is like your s6 except it has more internal storage. S6 only has 32gb iirc so now you hv double of what your s6 has on internal and also support external card.
What I do meant is apps do not install itself to the external storage unless you force it to.. some games with alot of data allows you to choose where to install while some requires you to go to the Settings->Apps on the apps page go-to storage and choose to install to external sdcard. Not all apps support this feature (especially not system apps). Besides, it is not advisable to install all apps on external becos it is alot slower than to run from the internal. People usually install games on external becos of it's large data set but for the normal day to day Apps, it's best to keep it in your internal for better performance