The editor does not use .txt files. The editor uses .stats files.
Mods are not distributed with .stats files, so you can't see their data in the editor.
If you can't see their data in the editor, you can't even copy the table as tab-delimited rows that you could paste into your table.
Also, we're not sure what the
{table}_{table}.txt files do since they're used by neither the editor nor the game. The .txt files in the Generated folder are generated from the .stats files when you save the table, and only those .txt files are used by the game.
Long story short and simplified: you have to manually add that data to your mod, or get the mod author to send you their
Editor\Data\{mod} folder, which contains the .stats files for their mod.
Related:
Editor does not refresh .stats files