I don’t know if you can make folders on steam but on my Xbox one I make a folder of started games and at max start 5 games when I finish one Ill allow myself to add another but no more then 5 I try to do this on each system (this is what i use to do)
If you have a very short attention span or lack focus in games another method I use is only fill your steam with a tb of games (even if you have a bigger amount of space this is to limit yourself) and don’t download anymore games until you have say half a terabyte free space that way your playing what you have downloaded and can flip between games to focus on what you have already installed (you can always still buy games just dont download them until you’ve gone through half your storage! :) )
This is what’s been helping me
Weirdos eating a keyboard