Finished

The issue addressed by this PR is almost 10 years old. #67407 proposed some changes, but there are still some issues, such as the shortening of "regular expression" to "regex" not being accepted. The main issue addressed by this PR has not changed; most of it is about the proposed changes, and modifications have been made according to Terry's suggestions #67407 (comment)

Here are the before and after screenshots:

IDLE is a program with a long history. Overall, this PR makes various changes to modernize the user interface of the Find, Replace, and Find in Files dialogs:

• Got rid of the "close" button, since it is redundant.
• Moved the buttons below the text fields, to make better use of screen real estate.
• Shorten the titles by getting rid of the "Dialog" part.
• Renamed "Search" title to "Find" to match the menu item.
• Added slightly more padding.
• Removed the "Replace+Find" and made "Replace" have this functionality. (all modern editors use Replace to mean "Replace and Find")
• Change replace dialog button [ Find ] to [ Find Next ] (terry)Modernize the IDLE Find/Replace/Find in Files dialogs #67407 (comment)
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Others

Also see my another IDLE PR (Should be after this pr merge) #121420

• Issue: Modernize the IDLE Find/Replace/Find in Files dialogs #67407