Question

After uploading my GEDCOM file, I've made changes and want to upload again to reflect changes.

Answer 1

See this help page.

You can't update your tree with a new GEDCOM, because that could overwrite the work of other WikiTreers.

On the other hand, if you've added a new branch to your tree, that doesn't already exist on WikiTree, you can upload that as a new GEDCOM and attach it.

Comments

Side-note: Adding new branches is now easier with GEDMatches. If you're very careful, you could upload your full GEDCOM but then use the ancestor Multiskips to skip everyone but the one line.