I saw your post and thought it would be fun to try and make a basic system for attaching to walls and I came up with one that only uses around 10 events if you don't count basic player movement and 4 instance variables.
The way it works is wherever there is a wall in your level Add a tiny trigger area object to it, and in game press cover activation button and I recommend you make a layer for triggers so you can hide them when you're designing the level each trigger area has a variable called side which can be 1 or 2, 1 is for any wall that the player will attach to from the top or bottom of, two is any wall that the player will attach either from left or right side of.
This system doesn't pin the player to the wall what it does is it limits their movement relative to the walls position and won't let you leave the wall until you either leave the trigger area on the wall or press the cover activation button again, and if you want to set up a system so your player can't take damage in cover there's a built-in bool called attached to wall, that you can put in your take damage condition.
This is a base to build off of hope it helps, and good luck with your project!
If you have any questions just send me a PM