There are a variety of apps that might do what you want, or at least some of what you want. I don’t use most of them, so all I can do is pass on what I’ve read/heard.
Built in:
Shortcuts can access the clipboard both for input and output. It also has regex (
Regular Expression) support, so some pretty complex text manipulation is possible. You have to copy text, run the shortcut, then paste the results, so not as easy as it could be. You also need to learn regex expressions, which has a fairly steep learning curve.
However, lots of things are possible without deep-diving into regex.
I have a couple of shortcuts that format and save the current time or date in the clipboard. I use them when I want to time and/or date stamp something in Notes or other apps that don’t have their own time/date functions. They use the built in Calendar actions.
The Keyboard Text Replacement built into iOS are decent at substituting text for other text. Two of the default replacements will turn ( c ) (spaces added to defeat replacement) to the copyright symbol © and ( a ) to . Settings > General > Keyboards > Text Replacement. Easy to use, but limited in power.
Apps:
TextTool 2.0 is a text editor with a lot of built in text transformation tools. Got a pretty good review from MacStories.
TextExpander is like Text Replacement on steroids. Rather than replacing short words or phrases it’s meant to insert entire paragraphs of boilerplate text. It provides it’s own keyboard which you can add and use in almost any app.
There are also text editors that have built in scripting, based on a variety of languages like Phython and Java. Three from memory are: Editorial, Drafts, and Ulysses. But that’s from memory, so I could be wrong.
The only one I own is Editorial. It has a fair number of workflows (as it calls them). Most are automations for Markdown. I’ve barely used Editorial, an never the workflows; so I’m not recommending or not-recommending it.
Good luck.
