completely new to GIMP and I am wondering how to remove a filter I've added to an image. I used one of the light and shadow filters and I can't undo it. Is there a remove filter or delete filter option? To remove it from the image.
In GIMP filters are not added, they are applied to the image content. Thus there's nothing removable. If pressing Undo doesn't any more restore the content and you haven't a spare copy of the modified layer, you are out of luck.
For future: Duplicate layers under work and save often. Use "Save as" and give a new name to have older versions available if needed.
You can't remove a filter once has been applied unless you are still able to use Undo (Ctrl+Z) to go back to the point before you applied the filter. If you have saved and closed the document since you applied it, then reopened it, Undo will be unavailable because the History states aren't saved within the XCF document.
There is a way you can work around this problem, but you have to make some effort to implement it in your workflow.
You can click Layer > New from Visible before you apply a filter. That way, if you ever want to remove it, you can simply delete the layer, and the other layers will be unaffected.
The GIMP developers are working towards implementing better non-destructive ways of applying filters, but this is still some way off.