Nostalogic
Some idioms include: in second childhood lost a few cards from their deck a few cards short of a deck a couple jokers short of a deck not all there broken down over the hill having a senior moment lost in space talks to trees living completely in the past way past his/her prime
There are many idioms and phrases for 'on the back burner'. Some idioms and phrases for 'on the back burner' include 'pushing aside' and 'procrastinating'.
"Idioms for Being Afraid", "Idioms for Being Angry", "Idioms for Being Happy" are some examples of idioms found in the book "Found" by Margaret Peterson Haddix.
There are many good websites for idioms. I am currently looking up idioms on usingenglish.com. There are also some helpful explanations on idiomconnection.com. You might try english-at-home.com as well. Many online dictionaries also have an idiom section.
Some websites that have idioms written in them include The Free Dictionary, Cambridge Dictionary, and Phrases.com. These sites provide definitions and examples of idioms to help users understand their meanings and usage in context.
Here is a link to some idioms. You can pick the "non-common" ones for yourself -- some people have heard certain idioms a lot and others have not heard the same ones, so you'll need to decide that part.
savvy, brainy
The best place is to go on your search engine and type in "list idioms" You can also look at this question for some examples.
Some examples of idioms in "Divergent" include "jumping off the deep end," "barking up the wrong tree," and "walking on eggshells." These idioms are used to convey deeper meanings or emotions within the story.
cry unclemonkey's uncle
In a pickle