I made and intro for a video that I would like to copy and past into a new video, that way I can keep all the edits I made in the previous project. How can I do this? Each time I try, I get a warning that associated files can't be found.
What you need to do is create that opening sequence as its own project and render it.
Then add the rendered file to each project you want to use it in.
Have you moved the assets? NLEs don't store media files in the project file, only "pointers" to where the media is stored.
How are you trying to move the intro over? In general, you cannot load an Editor Timeline into another project. Composite Shots can be saved and loaded into other projects. There is a feature in Hitfilm called "publishing" which lets you save a Comp Shot into the Templates menu.
Publishing starts with saving the Comp so this tutorial will show you how to save and load Comps and set up a published Template.
The disadvantage to saving a single Comp or Publishing a Comp is you are limited to a single Comp. Comps that have been embedded/nested in the "main" Comp are not saved by this method.
Any and all Comps in a project can be loaded into another project with the "Import Composite Shot" menu by selecting a PROJECT file. A menu will pop up allowing you to select any/all Comps you want imported. What's nice about this is if you forget to select an embedded Comp that's needed it will be loaded automatically.
In your case - assuming your intro is built in Composite Shots, try using the Import Composite Shot menu and select the original project with the intro.
If you have moved the original media files, if Hitfilm can't find them a menu will pop up with the missing files listed. Double click a listed file, navigate to where it is, then select the file to reload it.
If you've deleted the original media, I hope you've backed it up to another drive. Again, Hitfilm does NOT store media in the project file, so, if you deleted the original media files and don't have them anymore, you're out of luck.
The issue is the intro changes each time because I add in different quotes for each video. So I had the bones from my edit that could be adjusted. It wouldn't work with exporting video. The audio and music would overlap. I also had png cuts to allow or remove longer segments.
If I could copy and past, then all I would have to do is adjust the dipping between the new clips and remove or add png clips to adjust for length.
I didn't use any composite shots in the original. I find editing in a composite shot much harder than in the editor. I tried to make a composite shot after, but it wouldn't let me copy and past my edited clips into a composite.
Also, I did import all the original files used into the new project, but I still had errors.