Question: There are some keywords I search frequently for throughout my project. I would like to use search like this: I put some keyword into the "register", after a while (I may or may not use regular search during that time) I want to search for that keyword in the currently open file. So I load it from the register and then `n`/`N` movements work like usual, just that they search for the keyword I have loaded.

Is that possible?

Answer: 
Try `q/`, this will open a window with your search history. There you can pick a pattern, edit it, and it will get run when you press `Enter`.

On a side note: `q:` opens a similar history window for commands.
You could put the keywords in a file and then `:source filename`. But generally when searching it's easier to hit `/` and then use the up/down arrow keys to use previous search terms.