You can access the Blog Hub
by clicking here. You can post one, but.....to be honest, blogs are largely being phased out on PC, which is why they aren't easily accessible/visible these days.
You can log Pokémon related challenges in the
Travel Journals section.
Non-Pokémon challenges can be logged in a Journal in
Video Games for that- check out
this post here. (You could update the thread title as you change challenges - e.g. updating it from "AgentInteleon009's Majora's Mask Only 3 Time Resets Challenge" to "AgentInteleon009's Minish Cap 3-Heart No Death Challenge")