Arts idioms
Arts idioms referred to the terminology or idioms originating 
in the subject of arts and music.

Drama

"Break a leg" 
Telling someone to break a leg was a counter-curse said to performers before they went onstage. 

In 2369, Deanna Troi told William T. Riker to break a leg the day before his big performance in Frame of Mind. He then replied that he'd "try not to take you literally." ()

In 2375, just prior to The Doctor's taking on the role of President of Earth in The Adventures of Captain Proton to acquire the aid of photonic lifeforms who believed the events of the program were real, B'Elanna Torres told him to break a leg. ()

"Bury yourself in the part" 
To bury oneself in a part was to become overly immersed in the role one was playing.

In 1986, when "Professor Scott" referred to Leonard McCoy as his assistant while visiting Plexicorp, McCoy warned him not to bury himself in the part. ()

"On cue"/"Our cue"/"Take a cue from"  
To do something on cue was to perform an action upon command or prompt. One's cue was the prompt in question, while to take a cue from someone was to do something that they would do.  

In 2369, George Primmin explained his strategy against Rao Vantika by saying he took a cue from Odo's earlier actions against him. ()

In 2372, Quark guessed (wrongly) that Lenara Kahn performed a sleight of hand trick involving an egg by swallowing it prior to entering Quark's and then regurgitating it on cue. Jadzia Dax informed him he was incorrect yet again. ()

Later, Joseph Sisko suggested that a smart Shapeshifter would absorb the blood of a poor victim and release it on cue when a blood sample was called for. ()

"Stage is set" 
The stage is set meant that the correct scenario/ was in place for an event to occur.

In 3074, a copy of The Doctor left behind on the Kyrian and Vaskan homeworld acknowledged that their simulation of 's encounter with them was at least founded on reality, if not true to it, saying, "Well, the stage is certainly set, but I'll have to rewrite the characters and revise the  a little." ()

Literature

"Read someone like a book" 
To read someone like a book was to be able to immediately know what they were thinking.

In 2376, after a newly resurrected Lyndsay Ballard felt she'd crossed a line by referring to herself as dead in front of Harry Kim, he dismissed her belief that she'd misspoke. She then reasserted her belief, saying, "Just because I've been gone for three years doesn't mean I can't still read you like a book." ()

"Take a page from one's book" 
To take a page from one's book was to do something that the other person would do.

In, when informing a version of Kathryn Janeway from another timeframe about Seska, Chakotay recommended that when dealing with her, they ought to take a page from Janeway's rulebook, by attempting diplomacy. Janeway added to the metaphor by saying that the next page of the book necessitated a backup plan should diplomacy fail.  ()

In 2404 of a reality where Voyager returned to the Alpha Quadrant in 2394, Lana and the Doctor (aka "Joe") eloped, an action which "Joe" described as being taken from fellow romantic Tom Paris's book. ()

Music

"Fit as a fiddle"
To be as fit as a fiddle was to be healthy.

In 2369, Rao Vantika, while inhabiting the body of Doctor Julian Bashir, assured Miles O'Brien that Bashir was still fit as a fiddle, despite his being unconscious so that Vantika could use his body. ()

"Music to my ears" 
Something which was music to (one's) ears was an occurrence or sound that one found pleasing.

In 2372, Quark described the 72 decibel ambiance of Quark's to be music to his ears. ()

In 2375, Kasidy Yates found Benjamin Sisko's welcome home greeting to be music to her ears. ()

Later, Vic Fontaine called the popping of a champagne cork music to his ears. ()

"Play it by ear" 
To play (something) by ear meant to rely on one's sense of  to learn how to play a piece of music, rather than sheet music. Metaphorically, it meant to improvise based on the way a situation was proceeding, rather than follow a pre-determined plan.

In 2152, Jonathan Archer told T'Pol that after he had secured Shran's trust, he would play it by ear from then on. ()

"Singing a different tune"
To sing a different tune was to have a different opinion about something than one had previously expressed.

In 2267, when Korob asked to learn something of James T. Kirk's science, Kirk was surprised by his newly conciliatory attitude, and noted that the man seemed to be singing a different tune. ()

Visual arts

"Paint someone" 
To be painted a certain way was to be portrayed a certain way, as if in a painting.

In 2269, James T. Kirk found an Excalbian recreation of Colonel Phillip Green to be different than history painted him; namely, wishing to avoid conflict and leave without further incident. "Green" noted that "History tends to exaggerate." ()

Slang
Arts