On my Wii U, I can easily move games from the internal memory to the external device (or in the other direction).

On my Switch I can't find this function to move games between the internal memory and the microSD card.

Neither can I decide to install an eShop game on the internal memory as long as the microSD card is inserted.

Am I missing something or is that feature not included yet? Is it announced for the next firmware update?

not a feature atm no :(

its not possible at the moment. for now if you really want freedom to move your stuff around then save everything to a microSD card and then start storing data on a PC when it gets too full

I don't want to waste the faster free internal memory. So I just extract the microSD before downloading stuff I want on the internal memory (so far only Fast RMX) and insert it after that.

A bit inconvenient, but no biggie.

Physical is also slower than the internal memory. Also some good games aren't available as a retail version.

Curious, why does it matter?

From what I know the Switch is locked to how it uses internal vs external storage and I've read no where that there is an intention to change that.

the speed tests show that the internal storage is only slightly faster than loading from SD so unless you are really nitpicky about that kind of thing its not really necessary. plus Switch games have relatively fast load times in general. 

It matters next year, when my 64 GB microSD is filled up while I still have >20 GB free internal memory. Why waste that free internal memory and only use the external memory?

It matters even now for the games I want the shortest loading times possible: http://www.eurogamer.net/articles/digitalfoundry-2017-best-microsd-cards-for-switch-loading-time-comparison_7