Thick as thieves
Joined at the hip
Like two peas in a pod
a friend in need is a friend in deed
a friend in need is a pain in the neck
with friends like this,who needs enemies?
i keep my friends close and my enemies closer.
never borrow money from a friend,if you want to keep the friendship
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'.
One reason why some idioms are confusing because the way the sentences are worded
"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.
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.
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.
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.
Nostalogic
cry unclemonkey's uncle
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There aren't any that I know of.