In this case, it's exactly the correct word.
ap·pend
/əˈpend/
verb
add (something) as an attachment or supplement.
"the results of the survey are appended to this chapter"
And you see it a fair bit in other types of software, where you want to join something. Like video files, etc.
'Import' chunk would just be bringing a chunk in that's currently of a non native format... from 'outside'... And it'd be just opened... You specifically want to add something to something you have open already... so you 'append'. The import would close the open file and import the non-native chunk.
So...
Can we please get some tooltips added? Not just in every dialog box and preferences pane, but if possible to the menu items?
Then if we hovered our mouse over the File - Append... menu item, it'd pop up with a tooltip saying:
Append...
Appends existing Metashape
project file to the current one.
Useful for merging chunks,
or just combining cameras, etc.
I added the examples...There are so many features in Metashape... And it's not obvious what they all do. Especially if English isn't your native language.