I got even more pissed, you can't do anything with the Switch with the controllers on, while it is in the dock.
Again, grrrrr....
Fortunately there is a much easier way! ...The way I play it mostly is in GamePad mode (where both JoyCons are attached to the tablet, and the tablet is the main screen). That way your JoyCons are permanently receiving power, and getting charged whilst you're playing, as your JoyCons get charged from the tablet itself. The JoyCons themsleves don't actually require much power, yet they hold a charge way longer than the tablet does. But even if your tablet runs out of battery, there's a really easy way to solve that aswell...
You can take the power supply from the dock and use it directly on the switch so you can use it while it's charging.
Also if you have a newer laptop that uses USB-c to charge, you can use that power adapter to charge it as well.
Was just going to say the exact same thing! The power cable plugged into the tablet, with the joycons plugged into the screen, and played in handheld mode, means it doesn't even need to be docked, and you can play continuously without ever having to worry about the battery, and its' charging the whole time whist you're doing this! (that's pretty much how I used to play my WiiU anyway whenever the GamePad battery died mid-play during a long session, so it's essentially the same thing, just on a Switch!)
One other thing to note though, there was an interesting power experiment done I saw on a YouTube channel called TheKnow. What they found was, although the power socket on a Switch is USB-TypeC, so any TypeC cable will fit it, that you should use the actual power adaptor that comes with your Switch to do that if you need to charge at the same time as playing, as the adaptor provides enough power to do it, whereas cables alone do not. (apparently using cables alone does still work, just it takes a really long time, so the actual power unit is quicker because it's powerful enough to handle it).
The video I saw about this was quite interesting. Here it is if you wanted to see it...
I'd recommend watching the whole video, as there is also some good stuff to know about testing using a switch with a portable battery pack, but if you just want to skip to the bit I was referring to earlier about using the home power socket instead of just a TypeC cable, then that part's about 3 minutes in.
Hope this helps.
😉