I have used the GCP Interface to tie GCPs to images. I loaded a file with Projection on first line (EPSG:4326) then a line for each control point in the following format delimited by spaces. Name Longitude Latitude Elevation. Long / Lat are decimal degrees and elevation in meters.
Brought in photos and tied to gcps using the + button and clicking on the gcp target in the photo and then the corresponding gcp in the right panel. I did this for all images with gcps in them.
I then went to the dashboard and loaded all images into my project.
Am I missing a step? How do you save the gcp_list.txt file?